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The Grand City of Melbourne

I was going to write a blog post about my Reposit Power hardware, but time got away from me. So instead, I’ll give a quick run-down of our recent family trip to Melbourne, as a blow-by-blow account would get swiftly boring.

It had been over a year since we’d been away anywhere (to New Zealand – go if you ever get the opportunity because its magical), and we didn’t have time to go anywhere too distant. I had been to Melbourne a couple of times in the last decade for very brief work trips, but my wife had not been since her childhood, and the kids not at all.

Melbourne is a city of nearly 4.5 million people, only slightly smaller than Sydney in population. The two cities are rivals in almost everything, from sport, to politics, culture, coffee, events, finance, corporate HQ count … the list goes on.

I’m not really going into the comparisons here, because its an extremely difficult thing to be objective about. I’ve lived in Sydney’s suburbs for nearly two decades now, and only visited Melbourne. Its like test-driving a car you wouldn’t ordinarily consider, versus taking a road trip in the vehicle you have trusted for years.

On a technical note, I must say that being away from home is rampantly kick-arse for exporting electricity. I unplugged and switched off basically everything except the fridge, and we exported about 95kWh or nearly 16kWh / day, even with a bit of cloud.

Currently my energy bill looks like being around 43 cents per day after the connection fee is added. We’ll see how long that holds. But back to the topic at hand…

Melbourne Transport

Melbourne has the SkyBus service to and from the airport. Reasonably priced, it gets you from the airport to the CBD or vice-versa, and then provides hotel door service transfers, which is excellent.

One of the advantages of staying in the Melbourne CBD is the Free Tram Zone, which is immeasurably helpful when you’re dragging a couple of kids around. The CBD of Melbourne is fairly expansive, and the free trams, including the city loop tram using the vintage models, is very handy.

Melbourne Tram1
City Circle Tram Route 35 – interior of the tourist tram

We mostly stuck to the free trams, with one trip outside the CBD using the myki card system instituted a few years ago. You can buy a myki visitor pack at any 7-Eleven or appropriate transport hub.


The apartments we stayed in were at Mantra On the Park on the north-east corner of the CBD, just across from Carlton Gardens. While it cost a little more to get a room facing the park, it was well worth it, to wake up to that view every morning, and go to bed with it at night.

Melbourne ParkDay Melbourne ParkNightAfter arriving and getting settled in, the first item on the list was to establish what was nearby. As it turns out, in Melbourne, nearly everything is nearby!

I’ve stayed in some cities where your “centrally located” hotel is actually in part of town that shuts down for certain days or the week, or even entire weekends! Melbourne seems to just cruise right on through, with only small changes in the opening hours, if at all.

Food Options

Our apartment complex was just off Chinatown, and Melbourne seems to have this thing with dumplings that I am completely down with. The issue was time: how to sample all available dumplings, given less than a week in town?

On the first night we decided to experience Lygon Street – its a real Little Italy of restaurants, sometimes aggressively! The signore are out on the street, looking for your business, and always with a story.

As my wife’s family has a strong Italian connection, we decided to stop at Pasta Rustica Ristorante to sample the gnocchi. Nobody left disappointed, though the waiter looked at me sideways when I only ordered a small portion. I did it knowing my kids wouldn’t eat all theirs.

Lygon Street is packed with restaurants, and if you like Italian food, its the place for you. Later in the week we returned and tried the more modern Copperwood Restaurant, who produced pork belly so delightful I can’t do it justice in words. The pizza crust was also excellent.

Back towards the city proper, it seems like there is a great bar every block, a Bourke Street packed with options, and tastes from across the world to delight even the fussiest gourmet.


The decision was made to break our trip up into the days we had available, with one day being spent on the north side, one on the south, one through the middle, and one left for other things we’d pick up on the way.

We also put in some time seeing the Australian production of Matilda, which was a slightly sneaky gift to my daughter who is a massive fan. It did not disappoint in any way. Superb writing, music, lyrics, and casting. Alone, this made the trip worth it.

Melbourne Matilda

We visited the Melbourne Museum, which in addition to all the natural history you’d expect (animal skeleons, taxidermy, biology, geology etc) was running the Jurassic World display for a little extra.

The multimedia displays were of high quality, and the animatronic dinosaurs were top notch and scared the hell out of my daughter.

Melbourne Museum Jurassic World

The eggs above have a QR code on them that actually works. There was a charging T-Rex, an Indominus Rex and various others. I’ve uploaded videos to my YouTube Channel so you can see them there.

Melbourne StarMelbourne features two hi-rise platforms for getting a bird’s eye view of the surrounds. The Melbourne Star Observation Wheel on the northwest end of the CBD is probably the lesser of the two, with a wide open view across the Yarra Valley, but not much in the way of city sights.

Melbourne Eureka SkydeckA better option is located on the very metropolitan Southbank, called Eureka Skydeck, and gives a great look into, and over, the CBD as well as the parklands surrounding Melbourne.

To the southeast of the city you can see the famous MCG and Rod Laver tennis arena, along with AAMI Park. These three venues show just some of Melbourne’s sporting heritage, and its claims as the sporting capital of Australia.

The MCG hosts over 90,000 people, with big attendances for traditional rivalries in the Australian Football League. It has also played host to rugby union, rugby league, and soccer (football) internationals, and is the pre-eminent stadium in the country.

Melbourne Cricket Ground





Compared to Sydney, which grew up on a colonial sprawl around the world’s most beautiful harbour, Melbourne had the opportunity to consider and plan the city layout. It has resulted in a well-ordered city that, at one point, was the richest in the world during the Gold Rush in the 1800s. The planning of the city has resulted in delightful laneways and various books and crannies on every block.

Some of these are typical, dumpster-strewn loading zones, while others are a riot of street art. Some have bred cafe districts, with glass and wrought-iron ceilings to shelter the discerning bean-lover. Yet others have evolved into upmarket malls with expensive products, displayed on suitably sparse, elegant shelving.

Melbourne Laneway

It really is something a bit different around any corner.

Old Melbourne GaolBack on the tourist trail, we hit the Old Melbourne Gaol, where Australia’s most famous Bushranger, Ned Kelly, was hanged. We took a tour of one of the original buildings and did the “get arrested” experience at the old Watch House used by a prior generation of Victorian Police.

The Gaol is interesting in that it saw use from the 1800s right through until 1929, and then again for housing military personnel during World War II, including a serial killer by the name of Eddie Leonski, a US Army serviceman, and serial killer, who I’d never even heard about until that point. History, kids!

We also took some time out to visit ACMI (Australian Center for the Moving Image), which catalogues a rich history of Australian TV, film, and digital art. It is a really interesting series of displays and exhibits, including some famous Australian films like Mad Max.

Melbourne ACMI

There is so much more to talk about, but I’m probably getting to the point of wanging on a bit too much. I don’t feel like we even scratched the surface, having only spent four days on foot in the CBD. Short of winning the lottery and doing it at my leisure, I don’t feel like I’d ever get through it all, because it is constantly evolving.

Suffice to say Melbourne is a lovely city, and well worth a visit if ever you get the opportunity. It has a rich history, a vibrant modern culture, and more attractions than you can poke a stick at. It offers something for everyone, even if its just relaxing in the beautiful parklands on a lazy, sunny afternoon.

Parliament Gardens Melbourne

Powerwall ROI in Prospect – Part Two

In Part One of the Powerwall ROI, I covered off some commentary about batteries in general, a sample payback case by Choice Australia, and some general comments on improving your electricity usage.

Now, on with the show…

My Powerwall ROI Calculation

When I was doing my analysis on the Powerwall ROI, I first looked at what that money meant to our family, in pure financial terms.

The easiest thing to do with it was nothing. Just leave it in our offset account against the mortgage, and help pay it down quicker. At the interest rate we were paying, the value was less than $750 per year.

If the solar system could beat that figure – and I had few doubts it would at current prices – then on a cash basis it was a better investment than my loan offset. The Powerwall would simply ice that cake by increasing self- consumption levels due to power shifting.

Yes, we could have also used the money for an overseas holiday, but once you get four flights and accommodation, as well as visits to tourist trap gift shops (those meddlin’ kids!) you’re not going to get too far with that money. The experience of holidaying somewhere new is great of course, but so is freeing up capital in future years. Particularly in an electricity market with inbuilt price rises.

Let’s get to the detail of my situation, to fill in some blanks:

  • 5kW in 20 panels facing NNW at pitch of approx 25 degrees
  • Expected solar generation 19.5kWh average per day
  • Household usage for 2015 = 21.9kWh / day
  • Single level, brick veneer house, corrugated steel roof.
  • Insulated sarking under all roof panels.
  • Ceiling insulation using glasswool batts to appropriate rating.
  • Wall insulation on external walls to appropriate rating.
  • 4 beds + study, rumpus, double garage
  • Also running a 31,000 Litre pool (unheated) with thermal blanket
  • Gas cooktop, gas continuous hot water
  • Electric oven, fridge, cold feed dishwasher, washing machine, dryer
  • Nothing excessive like a movie room.
  • Ducted air conditioning aka The Bane to my Powerwall’s Batman

Any more details is just inviting the burglars!

Household usage is particularly important to know for your situation, and to try out the efficiency measures I detailed in Part One as the first step.

After looking at the figures, I thought the simplest solution was to get the biggest system I could, with the budget and roof space I had. This would ensure those cloudy days could still give me a chance at filling the Powerwall and/or run the house.

When it came to the payback factor, I took what you might call a macro view of what the system could do for me. Rather than work out the small fry of feed in tariff and saved import costs, I added up all of our 2015 electricity usage.

After all discounts from my energy provider, this figure was $1920. This is strictly what I paid for electricity after adding all GST and removing discounts. The connection fee is a set cost I didn’t include (worth another $311 per annum).

The system cost was $15,990, and so, if it wiped out 100% of those usage charges, then ROI is 8.3 years (System Cost / $1920).

That may be optimistic for various reasons, so let’s say the system reduces usage by 80%, then payback time is 10.4 years (System Cost / $1536).

Both calculations assume my power usage remains generally steady, and that electricity rates don’t go up, and that my system performance doesn’t degrade.

“But it WILL degrade!” shout the Lithium critics. And they’re right.

Nothing is forever, and the battery will not support as much input and output over time, due to known shortcomings with lithium storage. The battery has a 10 year warranty, but it does have expected degradation built into that. That is one factor.

It is entirely possible that the generation capacity of my system on average might not stand up to the lab-tested 19.5kW per day for the ROI period. That is the second factor.

Conversely, those quoted lab figures (which work out to 3.9kWh per day per kW installed for Sydney) may not be accurate in the face of panel technology advancement e.g. power optimisers. I’ve asked the source for more details on those figures, like when it was last updated. I’ll keep you posted if anything happens there.

In addition, how would I ensure I consumed that 19.5kW amount on average every day? For most people, that is seriously difficult without some kind of shmick automation suite, perhaps reaching as far as IoT monitored appliances.

There is a third, and very important factor: over time, as my system performance degrades, electricity prices will increase. If our government brings in an ETS (Emissions Trading Scheme i.e. Carbon Tax) over the next few years, that will have a big effect.

So for the purposes of simple mathematics, I’m assuming firstly that the degradation will be largely offset by the increase in unit cost per kWh. And secondly that, some days I’ll need the grid, and some days it will need me.

Or at least accept me for who I am. She’s a hard mistress.

The other large assumption is that nothing will change about my power usage between 2015 and 2016 and that… Wait, can you hear that? It sounds like… yes! Its the approach of:

The PlanTM

Fire up the triumphant music, Jarvis …

You Have The Power To Change

(Pun intended)

In Part One I referred to Origin Energy’s pricing, and how people don’t tend to move utilities readily, or financial providers, or insurers. Its called “Lazy Tax” where they just keep jacking up the price, assuming you won’t go because of the effort supposedly required.

Powerwall ROI procrastinateIn electricity circles, it seems hardly worth moving, when one company might only be a couple of cents cheaper per unit than another.

When you factor in that 2 cents = 10% per kWh in a lot of cases, and multiply that by thousands of them per year, its a different story.

You can also capitalise on that with a decent discount deal, but be aware that the “XX% pay on time discount!” will generally not cover your connection fee, only usage.

My old power company was giving me “twelve” percent pay on time for usage. Three percent was calculated before GST was applied, and the remaining 9% after GST was applied. So it was more like 11.73% discount. The cads!

My Powerwall will shortly be moving into the Reposit Power pilot here in Sydney, and as part of that I’ve moved to Diamond Energy for my electricity provision.

Diamond Energy Powerwall ROI

As you can see from their website, they subscribe to green principles, including some initiatives relating to the financial side. In discussions with them I’ve found their customer service to be great as well.

The partnership with Reposit is a chance to launch some new tech initiatives (micro-grids) in the renewables area. So a lot of boxes are being ticked.

I was even more happy when I saw their rates – here’s a comparison to my old provider:

Item ex GST ex Discount Diamond Old Provider Difference
Price (cents) / kWh 19.35 23.61 -18.0%
Connection (cents) / day 74.95 77.63 -3.5%
Feed in tariff (cents) 8.0 5.1 157%

Not bad, eh? Of course, the rates will vary with usage, as each provider has set bands for pricing, sometimes calculated against a daily average amount. The old provider dropped their price per kWh slightly at each band, while Diamond go up slightly, and use a monthly band.

It reinforces that we need to use less power, and more thoughtfully. The bands for Diamond are: first 100 kWh per calendar month priced as above, next 240kWh per calendar month (19.95c), remaining (21.6c).

Based on known use since install, I should not import much more than 70kWh per calendar month (about 2 per day), so should always price against the lowest band. Famous last words?

I also receive a discount for paying on time and by direct debit with Diamond, and even though that percentage is smaller than the ~12% I received with the old provider, the lower base cost is winning the race.

The Balancing Act

Import versus export is another key stat from the table above. The feed in tariff for Diamond is a lot higher, as a percentage, than I’d otherwise get from a lot of companies, and combined with the lower pricing, has a lot more impact.

If I get 8 cents for every kWh I export, and pay around 20 cents for every kWh I import (once GST and discounts are applied), then my ratio for being cost neutral on usage is almost exactly 2.5 export to 1 import. Under my old provider it would be almost 4.5 due to their higher purchase cost and lower FiT.

Of course, there is still the connection fee charged every day, with any provider. To cancel THAT out with Diamond, I’d need to export 10.3kWh per day in addition to keeping my 2.5 ratio above!

Unlikely, but every little bit helps to get that ROI under 10 years. If, by some miracle (or more likely, Reposit Power), the connection fees are also wiped out, then ROI drops to less than 7.5 years.

A Moving Target

Diamond’s cheaper energy prices change my ROI calculation. I accept that, but at the time I bought the system, I was calculating off the old provider, so that is still the basis for everything I look at, moving forward.

This all assumes I keep using power at the rate of 2015. Several things have changed in that area, which tip the balance in my favour.

Firstly, my pool equipment got replaced in January. It was older than the house I’m sitting in, purchased through eBay according to the neighbours. As a result, it wasn’t terribly efficient, and I’ve since discovered plenty of issues with the pump itself after pulling it apart out of curiosity.

The new equipment will lower power bills due to smarter controller options and newer pump components, allowing it to run less hours per day, at a more efficient rate.

Note that I wasn’t planning it as part of the Powerwall install, and wouldn’t mind that money back in the ol’ skyrocket. C’est la vie, which is French for “I’ll take the good with the bad” I think. Language is not my strong suit…

The house has been fully fitted with LED lighting, which was only completely part way through 2015. Timers are now on the AV and computer equipment to help reduce overnight use, and get the Powerwall through to morning, hale and hearty.

The crimes of the ducted air conditioner are now on display for all to see. As a result we’re dealing with our ventilation with a bit more thought, and using other resources (love our Dyson fans) to regulate air flow.

I’ve been clear on communicating with the kids about leaving things running (TV, lights, PlayStations) when they don’t need them. Every little bit counts, and “Less waste = more holidays” is the mantra. They are on board and excited about it… or the holidays, maybe.

In Summary

We still have lives to lead. We’re still going to want to do things that involve carbon fuels, directly or indirectly (at least until I get my Model 3). Nobody has a good plan for commercial electric flight, though they’re having a red-hot go at it.

As a family, we’re just going to do it a little smarter with the things we can control.  More consideration for the budget, the planet, and the grandchildren I hope to have some day, in a functioning and more enlightened society.

That sounds a little disingenuous, when I just spent the last 4000 words talking about money, but this is one of the major things critics miss about renewables:

It isn’t about growing your own kale in a mountain retreat, seeking purification away from the evils of the rat race, while aligning your shakras. I’m not knocking anyone who wants to do that, mind.

Its a balancing act, because we can’t all just jump off the grid and leave a few users with the burden. Some of us will seek independence, or be forced into it to live where we want. Some need to live in suburbia because of our commitments. Many won’t even be able to afford solar hybrid in any case, until the price drops after the early adopters get the ball rolling.

The point is, we have options, and we should use them.

We can all contribute – in fact we’d bloody better! If we don’t start moving in the same direction on this, from the policy makers right through to the average citizen, we’re not going to have an environment or society left to worry about.

Long-term, with energy companies acting the way they are, and regulators supporting them, it will be up to us to take back control, and make sure we can improve things for our generation, and the ones to come.

I’d encourage anyone who can raise the capital to get into solar at the least, and look at battery storage as well. There are plenty of options hitting the market – check out the new gear from LG Chem, Redflow, Panasonic, and Enphase, just to name a few.

Oh yeah, and Tesla Powerwall! Can’t forget those guys…

Hopefully this information has helped you look at your own situation, in terms of considering a system, or you just find it an interesting perspective.

Moreso, I hope the motivation for buying a system – which ever option you go for – is beyond purely financial.

As always, if you’ve got any questions, ping me on Twitter.

Powerwall ROI in Prospect – Part One

There has been a lot of discussion swirling around about Powerwall ROI (Return On Investment) since the launch, and comparisons to other systems. People want to know what payback time is, and that is understandable, given it is such a large investment.

I did a fair bit of research into the financial side of this before going ahead. I discovered more about my power bills than I knew previously, such as the effect of summer on my consumption.

I started writing this post over a week ago, and once I got the rantmobile into gear, it was clear it would sail past 2000 words at a rate of knots, so this is Part 1.

[Note that since this post went up yesterday, the original link to Choice Australia’s analysis has broken intermittently, so I found a nicer one on the website of our national broadcaster, the ABC.]

Negative Waves

Any of you seen Kelly’s Heroes? Get onto that, if not, because its a classic. Donald Sutherland’s character is a crackup.

What does this have to do with anything?

On many sites that post about renewable energy, there are articles and references to Powerwall, or other lithium batteries. In the comments section of pretty much any of those sites, you can see people provide their own analysis, sometimes critical. The targets can range from Powerwall specifically, to Lithium Ion in general, or even Elon Musk himself.

Rather than pick a fight, I reflect on the fact that we’re at least having the conversation, even if we don’t agree. And it is quite an important conversation to have in the bigger picture of renewable energy.

Prior to 2015, the only people talking seriously about battery storage were those with a principal interest in the technology, like engineers, or those with aspirations (and money enough) to move completely off-grid.

grandpa Powerwall ROI

Relax – I’m just joking, offended people! Lithium may not rank as high as your favourite technology, but it still a valid player in the consumer market.

I know someone with a lead acid gel setup who paid 25% more than I did, got 4kW of panels compared to my 5kW, and has double the storage capacity. They only cycle half that storage capacity on any given day, which is a common method in the VRLA Battery arena, to extend the battery life.

Its just him and the wife, with no kids leaving lights and TVs on when they walk out of the room. He’s not using any grid power whatsoever, and has backup power any time the local grid, delivered by overhead power lines, get messed up by a storm.

It wouldn’t work for my situation as well due to space (his place is semi-rural), and I know other people in urban areas who would be put off by the Big Steel Battery Box approach. There is also the higher entry cost.

Before anyone dismisses me as a hater: I think it is a great system, and suits his situation well.

However, we can’t pretend any system is perfect in today’s market. If any one existing system was the ducks nuts, everyone would have it by now. There are pros and cons to everything, and consumer choice and circumstance will often determine what “best” looks like.

I don’t think the Powerwall is perfect either. It could have been cheaper, or had a bigger capacity, or made me coffee every morning. The thing is, it ticks the boxes enough to get my interest. I made the decision to adopt early with a fair idea of the shortcomings, that subsequent generations of the technology will build on. You have to start somewhere.

Buzzword Alert!!!

Importantly, the Powerwall is seen as a disruptor. Or a piece of flashy showmanship from Musk. Whatever.

While solar is still trending upwards, here in Australia there is a lot of uncertainty about the industry, even with the recent announcement of a $1bn renewables fund. Although that is really just the old fund, dressed up a bit in new clothes.

Widespread battery storage could be the next accelerant we need for this little fire, particularly because battery storage of ANY kind it isn’t exclusively tied to solar. You can draw off-peak power to reduce bills, and source that power from green generators, for example.

You will see several analyses out there that focus purely on the Powerwall ROI itself, with retrofit to existing panels. People will naturally look at what suits their situation. In the event they’re NOT in the market for a Powerwall, they might just look for the numbers that make their point best.

Occasionally that is them slinging mud, which is a shame. If you’re going to be critical, at least offer an alternative.

I’ve seen a few efforts to break down the payback time of a Powerwall, and that might be a useful analysis for someone who already has solar. I’m not entirely convinced their methodology is right, nor am I 100% satisfied that the system cost they quote is accurate, unless they’ve had someone out to deliver an actual quote.

Choice Article – Analysing the Analysis

Choice Australia and the ABC published an analysis for whole of system cost. On that link you can scroll down to the bit about What is the payback time for the Powerwall? There, you’ll see the situation for Andrew’s family, and their payback time.

Short version: somewhere between 14-24 years. Remember, it isn’t just Powerwall, that is entire system (4kW with Powerwall, installed).

This version also shows what would happen if Andrew used all his solar power, giving a payback time of 9.7 years. It is the first time I’ve seen an analysis actually admit the payback could fall inside the warranty period for the Powerwall.

There were a few points I found interesting in the analysis itself. Andrew’s children are a similar age to my own, they work from home arrangements, like I have, and live in Western Sydney, as I do.

The primary difference is that Origin Energy’s pricing is quoted as $16,500 for a 4kW system with Powerwall. That is less favourable than the $15,990 I paid for 5kW of panels with the same battery from Natural Solar.

Dividing the numbers simply per watt, Andrew paid $4.125 while I paid $3.198 – that’s an extra 29% hike per unit of generation capacity. Maybe the quality of the panels make a difference, though I’m pretty happy with mine.

It would be interesting to know how big Andrew’s house is. I assume from the article’s quoting of 38.4kWh that they have electric hot water and cooking. From one of the photographs in the article it seems like they have a split-system air conditioner.

I can see from pictures in the article that his house is of an older build than mine, which in a general sense has pros (smaller windows) and cons (older insulation).

It would also be interesting to know the following:

  • Size of house e.g. bedrooms as a simple measure, or floor space?
  • Do they run a pool, spa, or other external requirement?
  • Orientation of house and/or panels? Pitch?

All of this information is beneficial when other people are comparing their situation to Andrew. Its why I rave on about the issues with ducted air conditioning, so people are adequately prepared … *mutter* *mutter*

Choice quoted the average daily production of a 4kW solar system for Sydney, which is 15.6kWh. They use this to generate some numbers on power exported (feed in tariff) versus power imported, versus self-generated. Assuming all other measures stay the same, and come up with 24 years payback in the first instance.

Another calculation shifts the parameters, to maximise solar usage (trade their 6c export against saving 21.81c import), and come back with 14 years payback time – a 10 year cut, and not bad. It still assumes no other parameters change.

The Only Constant Is Change … If You Want It

My personal experience, and that of other people with solar, is that things don’t stay the same. Once you’ve got something attached to your house, capable of delivering free energy, for which you’ve outlaid some serious dosh, you start looking at everything you do.

Obsessively, I’ve been informed by unnamed sources…

I’ll bet Andrew hasn’t sat still – he and his family will be looking at ways to maximise their own efficiency and cut that payback time even further. Particularly with nearly 40kWh per day burned!

Electricity Provider

What you actually pay for your electricity is a big factor, and Australians tend to be slow when it comes to change for utilities (as well as insurance or home loans). It is seen as a hassle to move, when in reality it is easier than ever, and the market is ripe for competition.

I’m not sure if Andrew is required to stay with Origin as part of the installation, but given the premium cost of the system, I hope he’s getting a better deal than the quoted Origin rate of 21.81c/kWh ex GST, or at least a hefty usage discount.

Feed in tariff is proportionally low with any of the power companies in Australia that offer it, so 6 cents is not too bad for Andrew, when the market limit is about 8 cents for a new install in New South Wales.

We tend to look at our usage once a quarter when the bill comes in, and those paying by direct debit might not look at it, even then. Many will frown, and say they’ll do something about it, then life gets in the way.

As a first step, see what is out there in the market. Call your current provider, and see what is on offer. If you can get a better deal elsewhere, say so, because they may sharpen their pencil a bit.

Naturally, check the fine print. You may still be under contract with your current provider, and the percentage discounts may not stack up against base costs. Have a bill ready and know what your usage is, because most companies have tools these days to give you an apples-for-apples comparison.

Perhaps most importantly, take a look at whether there is a “green” option with that provider, and see what (if any) cost difference exists.


Usage efficiency is something a lot of people don’t think about, with a modern Western lifestyle. We just accept the lights will come on, and we burn the energy, and do things the way we’ve always done.

I believe there is always room for the average house to improve, and you don’t need to have solar panels to make some smart decisions.

Progressively replace your lights with more efficient options like LED. Halogen down lights, in particular, give me the irrits. They burn power like nobody’s business, and generate a lot of heat into your roof space.

The options you have with LED now include the same kind of warm white glow as halogen, and while the purchase price is higher, they last for years and burn less energy, creating less heat in the process.

Put timers on your non-critical equipment so they turn off at night instead of using standby power. I have timers on each of the major AV points in the house, to cut out at 11PM and come on again at 7AM. Digital timers allow multiple settings, so that you can also shut off the equipment when you’re all at work or school.

These things will cost you a few dollars short term, but pay off quickly in a rising electricity market.

Of course, a lot of modern audiovisual equipment is fairly good on standby, consuming only a watt or two when not in use. You still don’t need to pay for that, if you set it up right.

The move toward portable devices is also critical. Think about the content we can consume on a tablet or smart phone these days, which recharge at a couple of watts, instead of turning on the TV which might take 150 watts while running.

A wall plug vacuum cleaner can chew upwards of 1600W while running, and also impact what other devices you may be able to use at the same time.

A battery or cordless vacuum will use nothing while it is running, and charge with a much lower requirement over a few hours.

Big Ticket Items

Financially, it probably isn’t sound to just run out and get the newest star-rated kitchen appliances, but that doesn’t mean you can’t look at best-of-breed in the event they need replacing at some point. Make sure you understand the star ratings on your replacement, and what it will mean for your energy bill.

I mentioned that our oven is a little wonky right now, but to replace it is thousands, so we’re living with it, watching the sales. Spending an extra couple of hundred up front on a better oven could save a lot in the long run in power usage. And driving a hard bargain may save you now.

Outside the house, a solar hot water system is a serious consideration to replace existing electric or gas heaters. Government rebates are often available to help keep system cost down, and again, buy quality now to save long term.

That concludes the first part of this discussion on ROI. In Part Two, I’ll get into the bones of my Powerwall ROI calculations, embryonic as they are.

A Trip To Mount Kosciuszko

I thought I’d step away from the solar hybrid discussoin to talk about one of my other great loves, the outdoors. In particular, Mount Kosciuszko.

In Australia we’ve got a range of environments to choose from, though often you have to spend some time getting between them. The truly lucky live just up the road from some really spectacular places.

One thing we don’t have an abundance of is alpine areas. It surprises some people that we do get snow here, though its hardly widespread. And when you say “The Australian Alps” any European person who has seen them smiles politely, before looking sideways at each other…

Due to the age of the continent, the geological profile of Australia is fairly flat. Mountain ranges don’t tend to feature massive peaks, and instead have more gradual buildups to plateaus, like the alpine areas, or forested mesa, like the Blue Mountains, west of Sydney.

As an example, this is Mount Kosciusko, the highest point on the Australian continent, taken from Carruthers Peak, looking south:

Mount Kosciuszko
Mt Kosciuszko, 2012. (c) My brother for the photo. The arrow is mine.

Yeah. Don’t exactly need to take the crampons and ropes.

The Main Range Track walk from Charlotte Pass can be done as a 20km (12.5 mile) loop within a day, or you can camp overnight. It isn’t an easy walk in parts, with steep slopes, and the air is a little thinner between the starting point at Charlotte Pass (1835 metres) and the summit (2228 metres). Good fitness training.

It is a very different environment to a lot of other areas in this wide brown land. In summer, when the wildflowers bloom, the place is a riot of colour, in contrast to the photos I’ve featured here.

As we have a Long Weekend (Fri-Mon) for Easter in Australia, I decided to get cracking on Good Friday, and take my nearly 12-year-old son up for his first “Kosi” experience, and my fourth.

The drive from my home in Sydney to Charlotte Pass is a bit over 500km, or the better part of 6 hours once you factor in stops and traffic. This is territory I’ve covered many times, and I like to take the “back road” via the towns of Tarago and Bundgendore. It is a nice alternative to the freeway to Canberra.

We hit the trail at around 2.30PM on Friday, my son carrying my backup pack with 8kg in it, while I had 19kg in the main pack. For his first serious hiking trip, he struggled a little but resolved not to complain about it.

Kosi1As you can see from the photo, we took the shortest path to the mountain, via the service vehicle access track. The track was previously accessible by the public, but discontinued years ago due to environmental concerns.

In addition to the walkers and hikers, the service track is quite popular with mountain bikers, and at 8km with some decent inclines, will give most weekend riders a good test.

Temperatures for the day were in the low teens (Celcius) with a fairly stiff breeze that dropped it into single figures. Once you’re away on the trail though, with a long sleeved shirt you’re warm enough to keep going without issue. I have been up there in far worse, and only walked it once in patches of snow (November i.e. late Spring), from the other direction at Thredbo.

Though the wind picked up, we were making decent pace at around 3 kilometres per hour, enjoying the rugged views of the valley. Regular breaks allowed the boy to catch his breath and rest his shoulders.

Mt Kosciuszko

As we approached the drop into the Snowy River valley, the wind started to pick up, and we were running out of daylight to get to the top. My plan was to get up there, and maybe camp for the night outside under a fly with groundsheet. The wind chill was going to be a big factor without a proper hiking tent, or the lee of a boulder to hide in.

Old 3 Mile Marker to Kosciuszko Summit

A strategy presented itself at the river, when my son could no longer shoulder his pack. A long uphill from the river takes in the last 4.5km to the summit, and with a pack on my back, and one on my chest, we slogged up to Seaman’s Hut.

Once there, I decided to drop the packs, and head up to the summit unburdened. A quick dehydrated meal to get some energy back in the legs, and away we went. At 5PM we had about 2 hours of daylight and then an hour of twilight to find our way back.

Rather stupidly, I didn’t take water, torch, or emergency food. Fortunately none of those were required, though some snacks to assist my son’s flagging stamina might have helped, in retrospect.

rawsonA point of interest on the track is Rawson’s Pass, about halfway between Seaman’s Hut and the Kosciuszko Summit, which features the highest public toilets in Australia. This is the primary reason for the service track: regular maintenance of the toilet facilities, along with other National Parks and Wildlife Services duties.

Its built like a bunker, and a great place to seek shelter from the weather. A few years ago, on my first trip, the rain came in sideways, and we needed to stop in there to cook breakfast.

After a few more rest stops, sore feet, and chilled faces, we made it to the top. It had been hard work, covering having left Sydney that morning, but more than worth the effort, to see that smile.

Proud Dad moment

We only had about 90 minutes to cover the 3km return journey to Seamans Hut, and being downhill was thankfully the easiest part of the day. The sun was gone and the temperature was dropping toward freezing.

Back at the Hut, after 12 kilometres for the day on foot, we joined two fellow travellers – and here I’ll give a shout out to Ricardo and Ryan. It turned out that Ryan and I work for rival corporations, which was a bit of a laugh. Ricardo works in renewable energy, so it was six degrees of Bacon all round, and no shortage of conversation. The boy had his iPod loaded with Fruit Ninja to keep himself occupied.

Shortly after I got a fire going in the pot-bellied stove, we were joined by Peter and Casey, venturing out after dark, and we squeezed our bedrolls into place. Besides a few interlopers who turned up toward midnight, and were not able to be accommodated, it was chilly, but not unpleasant, even after the fire died out.

The wind howled out of the west all night, murmuring icy threats down the stove pipe, but we were warm enough, even if the sleep was fitful.

Shortly after midnight, the call of nature woke me. As the Hut is not equipped with bathroom facilities, I had to find a sheltered spot in that freezing wind, wearing only the shirt and trunks I slept in.

The reward for my shivering was beautiful beyond description. The stark beauty of the highlands, silvered and then shadowed at every angle by the moon, I could not capture with mere photography.

I knew it would be a beautiful day, come morning, and so it proved.

Mount Kosciuszko

Mount Kosciuszko itself is hiding behind that tor you see to the left of screen, with Seamans Hut in the foreground, and the full moon overhead. This is just after 7AM on March 26. For an old Nexus 5 Android phone camera, it turned out nicely.

The boy and I decided to explore a little, and get some of that dawn experience in, despite the chill of the breeze. The others were still sleeping so we had some time to explore the area, and marvel at the contrast of light and shadow.

The words grow short, as the pictures tell the story better than I can.

Sun on the hut shortly after daybreak
He’s thinking about Skyrim…
On the hill above the Hut, looking west toward Kosciusko (just visible)

After breakfast, we bid our new friends farewell, and headed back to the car. I stopped to get a picture of the Snowy River on our way out, but the crowds were building on a fine Easter Saturday, so it was time to make tracks and get back to civilisation.


I hope you’ve enjoyed this little side story away from the geeking out about Powerwall. Its nice to write about something else, and show people part of my country they might not have seen before. I recommend it if you’re ever in the area.

You can walk the 18km return from Charlotte Pass, perhaps staying nearby in Jindabyne if you want to day walk it.

The other option is to take the chair lift (fees apply) from Thredbo ski fields at the other end, and walk in 13km on the raised walkway.

Next time: Powerwall payback time, Part 1.

SolarEdge API Development

I haven’t blogged in nearly a week due to a lot of time spent developing an interface for the SolarEdge API. The idea is to display results in the PHP environment I have inside WordPress.

DISCLAIMER: this post will be mostly about nerdy developer things, with some added data analysis and chart talk. Apologies if your eyes glaze over; normal service will resume soon.

If you have any questions, by all means ask and I’ll do my best to blog about them or add to the System Specs page as appropriate.

Back to the (PHP) Future …

The last time I touched PHP was for my rugby club a few years back, with only incremental maintenance on that site since. I also had no experience driving API calls with PHP, or handling the resulting JSON, so there was quite a bit of a learning curve. Foolishly, I didn’t bother setting up a local environment to test, thinking I’d just pulverise it with my mad skillz.


The last 12 months at work was mostly concerned with learning NodeJS, which made my PHP a little hazy. They share some commonalities, so I’d keep using the wrong function calls. Throw in the minor differences between MySQL and my work DBs of PostGreSQL and SQL Server, and I had trouble getting things straight some nights.

Bad words were muttered. Repeatedly.

The results so far are a few charts that I’ll describe a bit later in the post, with more to come as I start to slice and dice the data I’m getting out of SolarEdge. Mostly, I laid down a foundation for data ETL (Extract Transform Load) that will allow future developments to be faster.

SolarEdge API Details

You can see the tech specs of the SolarEdge API in this PDF, but of course to use this you first need:

  • a SolarEdge supported system with appropriate firmware
  • an API Key from SolarEdge (generated by your installer in most cases)
  • your Site Id
  • a working knowledge of JSON (or the willingness to research it)
  • a plan of what to do with the output

SolarEdge users will know there is already a web portal they can log into to check their summaries and current power flows. It produces things like the charts I’ve used previously via screenshot:

SolarEdge API MarchWeek1-2

However, for some of us, logging into the portal can be a little tedious, and sometimes the data may not be as granular as we like. Perhaps we also want to compare it in different ways.

I’ve already logged a few suggestions through to the SolarEdge API development team, particularly in regard to battery-related data. It will help me develop new tools for Powerwall reporting in future.

Another thing to be aware of is regional differences. I was having a twitter DM brainstorm with a top bloke in Buffalo (hey Eric!) about the differences in data he was seeing. It appears that certain things we get in the SolarEdge Monitoring Portal in Australia are different to the USA.

I also know from personal experience that a previous firmware version on my SE5000 didn’t support monitoring of particular power flows.

Eric and a mate of his put up a GitHub Repo with some Google Sheets on it to pull data back. Recommend you have a look as they have good instructions and have cracked most of the eggs for that omelette.

SolarEdge API for UTP

My approach is a little more bespoke, because I’m of the opinion that my way is the best way, or at least the most interesting (*ahem*).

The SolarEdge API lists a limit of 300 calls per diem, which is fair enough, and I had PHP to get it, and MySQL to store it. After a bit of testing in Postman (REST Client) I settled on an initial strategy, to schedule calls every 15 minutes for two primary data flows in the SolarEdge API document.

Power Flow

/currentPowerFlow – a fairly simple summary of what power flows in the system, with source and destination mapped.

It seems to be used for this readout in the SolarEdge Monitoring Portal.

AC example

Source Graphic Destination(s) Notes
GRID Power lines LOAD Export is +ve, Import is -ve
LOAD House GRID Current consumption
PV Solar Panels STORAGE, LOAD Can feed both
STORAGE Battery LOAD Charging / Discharging

This data is it is not provided with a time stamp, which gives me a bit of pause; the accuracy of what this API call is doing against others with time stamps creates doubt. So I am making a few assumptions for now.

At present I’m using the retrieved data to track battery charge through both the fuel gauge on the side panel (to your right), and a battery charge line graph, which is not published on any other pages.

The latter operates on a rolling 24 hour basis, and was mainly done as a simple test of the WP Business Intelligence Lite plugin.

[wpbusinessintelligence id=”5″ type=”chart” iframe=”n”][/wpbusinessintelligence]

That said, its still pretty cool to know when the Powerwall got back up to full during the day. And its important to note that the SolarEdge API always reports “Full” as 98% and never above. I can live with that.

Power Details

/powerDetails is an API that gives power movement over a submitted time interval, broken down in 15 minute reads. This is a little different from the above, in that it doesn’t reference devices specifically, just the Watts that are flowing in the major categories of the system.

Term Meaning Notes
Consumption House usage Sourced from grid, battery, or panels
SelfConsumption Self use Usage covered by Production
Production System output Total of Solar PV + Powerwall output
FeedIn Export Power fed to grid
Purchased Import Power purchased from grid

The aim of the chart is to give at-a-glance notice of what is happening in the system, also on a rolling 24-hour basis. I have joined this data with some of the battery stats from currentPowerFlow.

And yes, I realise this is a mess, and will make it nicer in the coming weeks.

[wpbusinessintelligence id=”2″ type=”chart” iframe=”n”][/wpbusinessintelligence]

Joining data like that presents an issue, as they’re sourced from different API calls. As a result, there is no guarantee of accuracy because time-based joining of two datasets might represent different system states.

The fact that they run within milliseconds of each other is not quite good enough. You’ll see that inaccuracy borne out by “Powerwall Discharging” line spikes occasionally lagging behind the Consumption/Self Consumption spikes.

Overall, I’m happy if the “Importing” line stays near zero, and the “Consuming” line never goes above the “Consuming Own Power”. That means I’m catering for all my own needs with the system I have.

Tying it Together

There is little point to any of this unless you can automate it. I’m big on automation, and after building my own scheduler for PHP, I still didn’t have access to a cron-like tool with my current host.

Nor was I going to pay monthly fees to kick things off via Pingdom or other services – lack of capital, you understand.

Someone at work suggested using a Google Sheet script, with a per-minute trigger, to consume a page that simply called the scheduler function. Bam! Automation! Works pretty well, particularly for that kind of money i.e. zero dollars.

Total code base for doing this is about 480 lines of PHP total, excluding plugins for chart. I’m big on whitespace and comments, so its more like 200 functional lines.

Next Steps

There are some other APIs I’m looking into, and of course I’ll be thinking about new chart types in order to give some interesting insights.

I was also presented with a request, this very day, to make data downloadable in CSV or JSON format. That might have to wait until I’ve got a bigger dataset to report on, or more ETL running, or get a few feature requests done by the good people at SolarEdge.


Seeing these things in my own charts has led me to ask a few questions of the system itself. If I’ve got a near-full battery, and panels running hot, why am I ever importing power? My personal theory comes down to one of two things:

(A) Its a false read created by internal calculation errors, or inverter feedback of some kind; or

(B) The inverter, for whatever reason, isn’t responding to surges quickly enough to cover use from the solar panels or Powerwall.

I’m going to start keeping an eye on the smart meter I have installed to see which is more likely, based on the import/export it is reporting.

We shall see.


As I got halfway into typing this, I realised I hadn’t observed Earth Hour (19th March 2030-2130 hours) in any way. For the record, I only used 0.41kWh today, only a tiny bit of which was during Earth Hour.

Though maybe that was a false reading based on (A) above…

Energy Consumption – A Consumer Outlook

Though not generally a political type, some of the stories I am reading about the energy market give me pause for energy consumption into the future.

This seriousness will result in a mostly wordy bit of prose, quoting some people and websites more clever and studied than I, with no pictures (sorry).

The leadout story this week from my point of view was Giles Parkinson at Renew Economy, discussing the QLD regulator’s rejection of the increase to FiT (feed in tariff).

The findings of the QPC are not a surprise, given its past and current attitude to solar and the networks generally. It and other state-based regulators are criticised for seeking only to protect the interests of the incumbent network operators and gen-tailers.

There is even talk in the report of cuts to tariffs, rather than a holistic approach toward balancing energy consumption and transport patterns.

Those who consume energy can also produce it, after all. Clean power sold for energy consumption locally has a wide range of benefits, not the least of which is reduction in future infrastructure investment costs (which consumers will bear).

When you also consider the health benefits of low-carbon energy, you start producing a compelling financial argument beyond comparing (green) apples with (carbon) apples.

Big economies like China and India could derail The Paris Agreement for the rest of us, if they continue as-is. The good news is, those countries are considering implications beyond cost-benefit of network and employment, on behalf of their growing populations as energy consumption increases.

It would be grossly unfair if the West denied these growing economies, particularly in the Third World, a chance to power their nations. The question is whether we let them continue with old technology, or help lead them with new, to the benefit of all.

If I may digress gleefully for a moment, another article from Giles at Renew Economy has some of the best quotes I’ve ever seen in regard to Base Load power, from the Chairman of Chinese State Grid Liu Zhenya:

… fundamental solution was to accelerate clean energy, with the aim of replacing coal and oil. … the only hurdle to overcome [for base load power] is ‘mindset’ … there’s no technical challenge at all.

When you consider he was addressing a group heavily invested in oil and gas, that is solid gold from Mr Liu.

And yet, here in Australia we have campaigns running like Little Black Rock which purports to fly in and save our way of life. That is in spite of coal tanking globally, putting several projects by local and foreign companies under threat.

Indian company Adani, who were due to develop the massively controversial Carmichael coal mine, are looking to shift their focus to renewables, as one example.

Which brings me to the next in a long line of great article quotes from Renew Economy, this time in relation to something a little closer to home.

AGL is now working with 68 households in Carrum Downs, Victoria, to get a better understanding of energy management technology, solar, and storage.  The trial is aimed at reshaping grid usage through smarter use of devices, as Jason Clark from AGL says:

“If peak demand can be reshaped through minor changes to customer behaviour, network companies may be able to delay or avoid major investment that would put upward pressure on energy prices, while maintaining the same levels of supply reliability,”

This is a very interesting move from a retailer, and parallels a development in my own little world.

A few weeks ago, a nice chap from Endeavour Energy called to see how the Powerwall was going. After some general enthusiasm from both parties, the point was reached: they wanted data about household energy consumption as it relates to storage. They wanted my help to prepare for their infrastructure planning.

I’m usually pretty wary of these things, and I know some would be tempted to laugh in their face and bid them good day.

Yet, I agreed, and expect my install to be joined by others.

It is important that the infrastructure companies understand what is coming from a planning and engineering point of view, first and foremost. This will hopefully give them insight into how to most efficiently build future networks.

Stop sniggering, you lot. I’m serious!

I accept that the electricity retailers, in particular, will try and jack prices up in response to decreased revenue from people going solar at an accelerated pace. However, at the same time, purchase cost for solar hybrid will drop through research, development, and most importantly competition.

The next logical step for the energy triumvirate (government, wholesalers, retailers) would probably be removal of subsidies for renewables. This creates an environment where solar is suddenly more expensive, and so people stay on the grid, and state-based energy consumption.

I would argue that removal of subsidies is inevitable as the cost dives, and the government starts looking at penny pinching (they’re not going near negative gearing for a while at least). The only question is timing. Will the consumer market make this move possible before the electricity Illuminati ask for it?

(wait – elecminati? Uh… nope… )

Overarching all this, home electricity storage is moving into the mainstream. Large companies like Samsung, Panasonic, and LG are on board after seeing what a host of smaller ventures could achieve.

A suite of electric cars will be coming onto the market over the next few years, from mainstream manufacturers such as Volkswagen and Daimler as well as the continued development from Tesla, the Model 3.

Regardless of the engineering shortcomings of Lithium batteries pointed out by some very clever people, this isn’t a science fair. With apologies to The Simpsons, you don’t win friends with a big steel box, full of lead-acid gel cells weighing 50kg each. Consumers won’t go there in numbers.

If they did, companies like AGL would have run consumer trials years ago. Endeavour Energy wouldn’t ring nerds like me to see if they could, pretty please, get some data out of my system. The game has changed. A sexy, compact lithium battery with enough media coverage has seen to that.

In the near future, the government will have angry energy retailers on one side, and big corporates on the other, both looking for profits.

The government will have to start thinking, and hard. Particularly as consumers are presented with more, and cheaper, options for managing consumption of their energy.

And, just quietly, a penchant for throwing out incumbent governments…

We may have some short-term pain as our present members of parliament flap their arms about renewable energy, complain about imaginary wind farm illnesses, and so on. They have lobby funding to protect, after all.

This year feels like its going to be massive for renewables in Australia, and across the world. All it needs is companies like AGL and Endeavour Energy to continue to reach out to customers. At the same time, we should be involved willingly, to ensure that we’re getting a say or at least know what is going on.

Meanwhile, all of us need to start putting pressure on governments to get with the program. Follow websites like Renew Economy and One Step Off The Grid to stay informed about the news, views, and general interest stories.

Look at your energy consumption. Check your power bills and see if there is something better out there for you. Educate yourself, and others, to make a difference.

March Powerwall Update: Into Autumn

As per the tweet I sent the other day, my solar system has now generated over a MWh (Megawatt Hour) since it was installed in late January with the Powerwall. Essentially that means my panels have generated…

wait for it…

zoom in to close up …

Dr Evil

One Million Watts!

Yep, that’s lame, but I’ve been waiting to kick that off for weeks now. And some would say that picture has a striking resemblance to me.

On average that makes it a bit over 25kWh per day solar power generated, which is quite good considering we had a few cloudy days. Record day so far is about 33kWh generated, which might get broken around the summer solstice next year when the days are a bit longer.

March in Australia generally resembles February, but at this stage it is even warmer than usual in Sydney. You can read a really good summary at The Conversation about why its happening this year in particular.

I’m also following 9th Dan Chart-Master, Ketan Joshi on twitter, to see what statistical wizardry he’ll come up with next in terms of climate science and weather patterns. 

This record period above 26oC (79oF) has certainly provided some amazing solar power statistics for the first week in March, as follows:

Powerwall MarchWeek1

Fairly healthy rates for import and export, and its just a shame I’m yet to take advantage of feed-in tariff. I’m still awaiting changeover to Diamond Energy so I can take full advantage of Reposit Power with the Powerwall later this month. SO excited. GridCredits!!!

If I was on my current provider’s plan (which I’m not because I’d have to sign a new agreement), I’d have imported about $1.70 worth of power after all discounts, and made about $4.40 in feed-in tariff. Throw in 7 days of connection charges of $4.94 after discounts, and I’m $2.24 in the red, theoretically.

However, I’ve consumed 110.17kWh of my own making, or nearly 16kWh per day. That is actually pretty low against the household average over the year (~20) and if I didn’t have solar panels, that 110.17kWh + connection fees would be somewhere in the order of $31.70.

So really, when you think about it, I’m almost $30 to the good!

Importing just over 1kWh per day looks pretty spesh, but I’m here to tell you it could have been even better, and will be once this warm spell expires. Let’s go to the chart…

Powerwall March

Right at the start of you can see a little red block. This was an anomaly where the battery management firmware was confused by 29th February (Leap Day). Yeah, as a developer I can tell you it happens, occasionally. I’m assured its fixed, and because we’re on daylight savings time right now it started at 1AM on the 29th Feb and went through until 1AM on 1st March. Cool.

There is a big spike on 3rd March which was air conditioning going on for a very warm afternoon. On the morning of 7th March the battery finally went to sleep after the previous evening’s efforts cooking dinner and dessert.

Why burn stored energy doing all that baking in the evening? Firstly, it was a work day, but mostly, let’s just say that you can’t put obsessive battery monitoring ahead of my wife’s roast chicken, followed up by chocolate cake. You just don’t.

Our electric oven is running a bit out of kilter at the moment, judging by the noise coming out of the fan assembly. I’m getting that rectified next week, which should decrease duration of usage, by providing a more efficient cooking cycle. Moar cakez!

I recently added a new network attached storage (NAS) for backup duties, after the old one finally threw a shoe – i.e. one of its RAID partitions. The new one has power recovery so can handle being on a timer, along with the TV and games console running from that outlet. Only a few watts saved, but every bit counts when you’re trying to get the battery through the night as often as possible, under varying circumstances.

Powerwall Zen

As I’ve learned a bit more about the Powerwall, I’ve also tweaked some of the larger hardware pieces to exist in harmony with each other and the solar system in generall.

For example, the pool pump needs to be running for a certain number of hours per day to ensure cleanliness, and takes about 0.8kWh at standard operation. I’ve worked out the pump capacity (Qmax) and rate of flow correctly, to ensure I use only the minimum hours per day. I also figured out that running it later in the day allows the battery to top up earlier as the panels start cranking up the flow mid-morning.

In partnership with this, the timer on both our washing machine and dishwasher are set for the early afternoon, when the sun is at its highest. I leave a gap in the pool timer of 2 hours in the middle of the day so both these devices can run without issue, even when the sun isn’t so bright.

As always, a solidly overcast day can throw some of these plans out of whack, and that’s why a grid connection is a must. Beyond keeping the warranty of the Powerwall at 10 years (off-grid is only 4), in suburbia there is simply no reason to disconnect, with the grid as your fallback.

And I’m only a couple of weeks away from generating GridCredits, getting the battery topped up before the 2PM peak boundary makes sense both financially, and from the data it will provide to advance our knowledge of micro-grids in a modern urban environment.

Now, if you’ll excuse me, I smell cinnamon cupcakes baking…

Solar power through the square window

In my last post I alluded to having some thoughts on whether my house was making the most of solar power, particularly in regard to how I was using it. Knowledge is power, and the knowledge I’ve gained in the past few of weeks of my solar power usage has been very interesting.

Understanding which appliances burn the most power, what the usage patterns are, and the effect of weather, are all critical to getting the most out of the investment. This ensures that I can achieve the ROI I want, and that I’m a responsible user of any fossil fuel energy I’m required to draw from the grid.

March Sun solar power
Though the weather today was pretty good.

In all my analyses, the ducted air conditioner keeps cropping up as the villain (and at some point I’ll reconcile myself to that).

Its a difficult issue to address, as ripping it out of the roof space and replacing it with something else would just cost a load of money, and may not practically address the issue of solar power for cooling on a bang-for-buck basis. I need to ensure I’ve investigated other ways to either offset its use, or reduce my reliance on it.

Air conditioning comes down to a simple premise: comfort. You use it because you have too much outdoors in your indoors, so to speak.

That’s not a bad thing in the world of modern convenience, where our cars, offices, and houses are all air conditioned. However, have you ever thought that air conditioning is just treating a symptom of the main problem, and not the root cause?

The root cause – intrusive heat in this case – is going unaddressed. Even if you have a really efficient unit with all the bells and whistles, you may be able to do even better through other, more practical means.

Beyond “don’t leave the door open!”, there are many factors affecting your use of air conditioning or heating, often reflected in the design and quality of your building. Do you have adequate insulation of suitable quality? When was the last time you had it checked? Gaps around the doors? What about covering the windows?

Windows are a general weak point for heat transfer into or out of a building, particularly in large parts of Australia, where we don’t suffer the kind of harsh winters that require central heating or double glazing.

As a design point, a lot of modern houses here open up windows far more, which often results in more energy usage. One design element I need to deal with in my house are the large, west-facing windows.

About 8 square metres of glass, pictured at 1PM Sydney time today, before the sun hit

Both windows are in the same room at the front of the house, are 1800mm (6 feet) high, with the one on the left nearly square and the other about 2700mm (9 feet) wide, getting hit by sun all afternoon. The internal venetian blinds, while slowing the direct heat down a little, aren’t stopping it from advancing into the room in the first place.

Simple science: the sun hits the glass, which heats up, subsequently transferring its heat to the cooler air inside that is right up against the glass. That air rises (because heat) and more cool air is drawn against the glass. Rinse and repeat for 4-5 hours on a hot Aussie summer day!

Some people also look at tinting their windows or installing double-glazing to assist with this, but I remain unconvinced about either option in terms of value-for-money in most parts of Australia.

Tinting provides an extremely thin buffer, so it is only going to slow things to a certain degree – better than nothing of course, and relatively cheap compared to other methods. The downside is that in winter its going to perform the same function, stopping heat from entering the house via those windows. As a side note, the privacy aspect of tinting is lost when the lights inside are brighter than the lights outside i.e. at night when you are using that space.

Double (or triple) glazing is the architectural method of choice for sound proofing and insulation of glass. While its overall effectiveness year-round as an insulator cannot be questioned, the expense often makes the average home owner hesitate. Double-glazing in summer is best used where you can keep the internal temperature cool, and therefore stabilise the buffer between glass panes at a temperature somewhere between the outside and the inside. Generally speaking, if you’re not keeping the room cool through e.g. air con, the buffer will heat up, and start transferring that heat into the room.

In my opinion, and that of several electricity companies, the best way to stop this kind of heat transfer is to stop the heat hitting the glass in the first place. In essence, you create an external buffer zone where the sun’s heat and UV rays can’t get to the glass in the first place.

There are several options available, from adjustable fabric awnings, metal shutters, louvres, window shades or fixed awnings.

Rather than run out and spend a pile of money on anything custom-made for those windows, I decided to experiment first on our north-facing garage window. In the garage I have a network cabinet* in which I have my network backbone with appropriate patch panel for all the points around the house. I don’t want that equipment to overheat, and shielding that window should help prevent that.

* on reflection, probably a mistake to put it there, but it wasn’t going anywhere inside the house, according to my wife. Its called “compromise” I think…

Window coverings

Awning Solar Power
Fabric awning FTW!

I went to Bunnings Warehouse and, for the princely sum of $297, bought a fabric awning (1800mm wide, 2100mm drop) to cover the garage window from the worst of the heat. That’s it on the right, and I put it up myself in about an hour.

The awning can quickly be retracted in case a storm blows up, or in winter when I want the sun to warm up that side of the house. Sydney winters may not be harsh with snow and such, but we tend to have low tolerance for cold as a result 😉

I’m going to keep an eye on this for the next couple of weeks, as we move into cooler months, and see how it performs as the sun moves back north and puts more sun on this window.

Some (including my wife) may say that these kinds of awnings are a bit daggy, and yes you can buy them in stripy patterns if you want to be reminded of your grandparents’ post-war bungalow. However, if they do the job then I think for next summer I’ll be pushing to cover the rest of the problem glass on the north and west sides of the house.

It will be a battle royale between her Better Homes and Gardens and my New Scientist approach to this whole thing.

In the meantime, the best we can do is shut the problem room off during the heat of the day and let it become the buffer zone. My issue with that longer term is the electronic equipment in that room is under strain during that time from heat. And its the rumpus room for the kids, so now I have them in the main room watching my TV!

Garage door

The double garage door also faces west, and therefore gets a lot of heat in the afternoon. That was an issue from the day we moved in (late 2013), so after a bit of research I bought a roll of Green Insulation Reflecta-GDI which looks a bit like this once fitted.

Reflecta Garage Door Insulation

It definitely works – I can’t touch the bare metal of the door for more than a few seconds on a hot day like today (35oC / 95oF in the sun), while the insulation is merely warm , slowing the heat transfer into the space.

Measure your door panels before you order and, once fitted, you may need to recalibrate the garage door lifter to account for any weight change (it isn’t much but some units are sensitive). No adhesive required as it designed to fit most modern panel garage doors in Australia by sliding into the space at the correct width. That is actually a shot of it overhead – no issues whatsoever with staying in place in over two years.

While we’re on the topic of garage heat, DON’T close your garage door immediately in summer after you park the car in there. The heat you trap will radiate into the house through plasterboard before it will escape through brick or wall insulation. Leave the door up and get some air flowing through the place for at least half an hour.

Not so bad to trap that car heat in winter, but make sure the engine is off!

Solar Power Design – more than panels

If you’re in the process of building or renovating, you may have already made a lot of decisions around how you wants things to look. Some of those things may focus on solar power, while many more are about the right fittings, colours, and facade for your home.

Those with solar power aspirations will already know how important aspect is, though after discovering what I have about my own house, I believe it should be more than how many panels your roof can hold.

If you haven’t adequately considered the thermal efficiency of your home, you may not be capitalising on your investment properly.

Even if you’re not considering solar power for your house at this point, you might think about getting the place pre-wired while the build is occurring, as Jennian Homes in New Zealand is doing with all new builds.

Consider the design factors around your insulation (wall and ceiling) as well as windows and cooling or heating options. Sometimes these things can be lost when you’re focus is on the right marble bench top, or the right tapware.

The builder may promise the latest, you-beaut ducted AC, but it may end up costing you more over the longer term. Look instead at smaller, more efficient air conditioners (like split systems) to cool or heat the space you need. In either case, make sure you understand the energy requirements of these add-on extras and how they will affect your power usage.

A few little decisions now can save you hundreds or thousands in the future, particularly as prices rise (and they will) and governments feel pressure to adopt renewables standards across the world.

Powerwall Data Analysis

The Powerwall copped a hammering this week, with another really hot day in Sydney showing up to get everyone’s air conditioner roaring, and the good news is I can see how much.

The SolarEdge inverter I have (SE5000 model for those playing at home) feeds back data to their HQ, which I can access through a web portal. At the moment I’m just taking screenshots to log interesting events, and provide feedback to everyone in the chain.

As you can see, its great from a consumer perspective to understand your power usage at-a-glance, as well as the Powerwall and panels data. So I know this week how much I’ve exported, used on my own needs, and what I had to take from the grid.

SolarEdge Portal Powerwall

You can see that 25th Feb was the hot Thursday, with temperatures reaching 41oC in the shade. The ability of our family to tolerate that kind of heat is not pronounced, so the air conditioner goes on.

The big red spikes above the “4k” line represent our ducted air conditioner going on. Yep, its a hungry beast. Generally speaking, it seems to kick off around 5kW to run as an absolute minimum, and generally goes around 6kW, depending on the ambient (room) temperature versus the thermostat.

One thing I didn’t fully understand when I got my system installed was the power parameters. I have a 5kW inverter, that means the system can move 5kW from the panels and Powerwall as a maximum.

So, for example, if the panels are blazing and the Powerwall  is full, but I need to run the ducted air, it is going to pull a maximum of 5kW from my panels and battery combined, and then go to the grid for the rest. Like so:

AC example Powerwall
Running the ducted air conditioner

Yeah, bummer, right? Unfortunately, the house came with this A/C so there isn’t much I can do about it at this point, beyond mitigating my use of it and setting my house up a little better. More on that point in a later post, when I get more time to think about it.

So, back to reviewing the data, and let’s continue by just looking at the solar generation side of things – and to make it interesting, let’s drill down on the days leading up to the full moon (yes, the portal has a drag-zoom setup – its pretty cool).

Lunar Powerwall

So we have some nice, parabolic curves representing power generation during the day. The peak is generally around 2PM each day (keep in mind we’re in DST here) and quite often hits in around the 4kW mark. However, I’ve seen individual readouts above this. I guess the graphing software tries to smooth curves as often as possible.

This isn’t the best bit though – notice the little squiggles happening around midnight on each day? I’m told by the installer that customers have reported moonlight triggering the panels, and I guess, being photo-voltaic in nature they respond to any light bright enough. Yep, that’s right:


Here is a zoomed-in version from the night of the 24th Feb through to about dawn on the 25th, showing the fluctuations. Not much graph smoothing here!


I’m kind of geeking out over this, in case you hadn’t guessed. Sure it isn’t a lot of actual power (up to 70 watts), but you must admit, that is pretty cool.

But going back to the top chart for a minute, you can see from the 25th onward a lot of red readout in the low-levels, meaning the Powerwall has ceased covering “Self Consumption”. The day after was cloudy, so little opportunity to replenish the levels.

After some awesome sunlight today with a nice cool breeze (no air con!), the Powerwall is sitting around 70% to get me through tonight and beyond.

It helps that we were out today, not using much power, and having an awesome lunch at Barbuto Restaurant in Narrabeen, followed by a stint on the beach in the afternoon. Great day!

Barbuto Pulled Pork

Narrabeen Beach

Tesla Powerwall – hello? Is this thing on?

My name is Nick, and I had the privilege of the first Tesla Powerwall installation in Australia (maybe the world, they say). It has been a short, but very interesting journey so far, and as it continues I hope to share useful information, a bit of humour, and a hopefully less swearing than I provide in person*.

It would be remiss of me if I didn’t mention Natural Solar at this point. Chris Williams, Oliver Coleman, and the whole crew have been really helpful in putting my system together, and I’m seeing results already.

Tesla Powerwall
Oliver.  Credit: Hugo Sharp Photography

I’ve got all these grand ideas about what I want to do here, but I typed most of this up on a Thursday night, having come home from at work with little in the way of motivation after a 41oC day here in Sydney (106oF for any Americans reading).

Tesla Powerwall
Installation Day

You’ll have to forgive the absence of anything like style on this site. I am one of the least creative people you’ll meet in terms of design and UX in general. My job as a database guy is more about structure and numbers, and its a different kind of beauty…

The good news is, I know people who are fully conversant with the interwebs, and have great advice, which they will no doubt give, so this will improve over time.

I just thought it was time to get it started, and the best place to start is at the beginning.

*people who know me will be shocked if this turns out to be true…

Why did I install Tesla Powerwall?

There were many battery options out there already, but this one happened to fit my needs best, and I’ll definitely cover that in more detail in a future post.

The installation itself has been covered in a fair few outlets in the mainstream like The Australian/AFRNews Corp, Sydney Morning Herald. All of them seemed to have their own angle on Tesla Powerwall, and what its going to do for the planet, or their otherwise empty column inches that week. At least, those they’re not stealing from Huffpost or some random entertainment website…

Further coverage in tech sites like Gizmodo and Mashable got a few tongues wagging, as well as some extremely weird translations resulting in me being “aristocrat of a nerds” (seriously, read it).

Ultimately, there is a financial argument that underpins why I got a Tesla Powerwall (or any solar hybrid system) installed. Despite being accused of a “profligate Western middle class lifestyle” I’m by no means rich (and no steve f – if that is your real name – the pool isn’t heated). I earn above the national average, and am fortunate enough to have a smart, talented, hard-working fox of a wife who earns something similar.

Ultimately, I make no apologies for trying to enjoy my life while offsetting that with investment in renewable energy, but some people can’t be pleased.

Tesla Powerwall
The lads from Splice Electrical getting ready for the reveal Credit: Hugo Sharp Photography

Renewable energy investment makes up the second leg of the argument. There is a growing need for research and development into solar, wind, and other forms of power. We can’t keep burning things to make lights come on when we have, as Elon Musk said, a giant, free source of energy right up in the sky. All we need is the will to change.

The good news from my perspective, now that I’m following sites like Renew Economy and One Step Off The Grid, it is clear that this movement away from coal and oil is only accelerating, if we can get our politicians to listen for long enough.

The third part of my desire for this is sheer nerdliness. I’ve been watching Tesla for a while now, and what they’re doing is impressive under the leadership of Elon Musk. You can read about Elon Musk in a long and humorous fan perspective at Wait But Why if you don’t know much about him already.

In summary: Built Paypal, started Tesla Motors with the world’s sexiest electric car, and has this thing called SpaceX who launched and then landed a freaking rocket so they could re-use it later.

In any case, Tesla and SpaceX are working to improve our situation on this planet, and try to get us to other planets. If you haven’t watched the Tesla Powerwall launch, I recommend it.

For me, its about looking at the system and how I can learn more about it. Maybe there is a job in renewables that I can take my tech skills to? I don’t yet know all of what the future will hold.

What I do know is that I’m down with lower household running costs, a smaller carbon footprint, and analysing the data available to me from the system.