Sonnen Versus Human Nature

German battery company sonnen has entered the Australian market, with their sonnenFlat product. I would have written about it earlier, but I’ve been suffering a fairly serious flu that is hitting Australia late this winter.

On the surface, it looks like a fairly sweet deal. Add a Sonnen battery pack to your existing solar array (or buy that, too), and never pay for electricity consumption again.

In return, sonnen get to use the battery storage as they see fit via the concept of Virtual Power Plant (VPP).

There are a few conditions of course, as this article from Solar Choice’s James Martin II points out. I’d also urge you to also read the comments section as Solar Choice provides further information via responses.

My first impression on seeing the details: this is a mobile phone plan, but for electricity. You pay your $30 a month, use up to the “cap”, and then get charged for excess.

So what are the “gotchas”?

For The Provider

sonnen will make some money on battery retail, first and foremost. The consumer pays for the upfront cost of the battery system, as well as the ongoing payment.

In return, sonnen get a VPP, with which they can play in Australia’s energy market.

Sonnen Eco 8
Sonnen Eco 8 (via Natural Solar)

This may include direct retail of energy, but I don’t see it, despite their promises to “kill” the traditional energy model.

When the sun goes down there is no generation available to them as a standalone provider, and the battery users they are supplying “free” power to will take most available demand from storage.

Most likely, sonnen will seek a partnership with an existing generator and/or retailer. There is already talk of sonnen investigating agreements with companies like AGL, one of Australia’s largest energy providers.

There is a bit of VPP talk going around in Australia at the moment in general. It is one of the ways in which we’re going to address how we manage the grid into the future.

It is acknowledged that demand growth for traditional grid generation has tapered off due to a few factors. This includes better energy efficiency, and uptake of renewables behind the meter. Departure of some industries like car manufacturing also contribute.

However, the need for smarter demand management is growing, particularly where the consumption profile is changing for consumers and industry.

Simply put: we don’t consume energy the way we did in the past. Terms like “baseload” are swiftly becoming meaningless, and I’d urge you to place limited trust in people who say it is a priority!

For The Consumer

The obvious advantage is cost savings. By investing in a sonnen system, you can fix the running cost of your household for years, literally.

Paying $360 per annum for electricity would sound like a fairly sweet deal for most, particularly as some consumers have just seen price hikes of up to 20% in Australia.

There is the up front cost that could make the whole conversation moot. Like the arguments around leaving the grid altogether, capital outlay is going to be a deal breaker for a lot of people.

Caveat EmptoR

In one of the comment replies in the Solar Choice article, they note that the “cap” includes ALL usage in the house i.e. not just imported electricity. This starts at 7500kWh per annum for the $30 plan.

For the consumer who can afford the investment, and just want a set-and-forget system, that makes a lot of sense. The consumer doesn’t have to micro-manage the system, and maybe has the option of getting a little bit smarter about their usage to try and fit under a lower cap.

One real risk is for those users who sign up thinking its all about “free electricity”. If they don’t look after their consumption, it will start to hit the hip pocket, and quickly lead to consumer regret.

And what if your household doesn’t consume 7500kWh per year? As unlikely as that sounds with 20.5kWh to play with. What sort of plan do you go on?

It is critical to understand your consumption across the year, before deciding which system or plan to sign up to.


Does It Fall (sonnen) Flat?

I’m a consumer who bought a battery without a plan like sonnenFlat behind it. I took some actions to maximise that investment, particularly trying to ensure the house runs lean.

The statistics I’ve compiled bear this out. My consumption figure of ~16kWh / day via the system APIs is lower than the ~21kWh / day I took from my billing data.

The less I consume, the more I can export, which produces direct financial benefit for me. I’d also like to think it lowers my carbon footprint a bit.

This is a secondary problem I see with sonnenFlat: you don’t get any benefit from being smarter or better about your energy consumption. Where is the incentive to use less?

To me its a similar argument to those people who are on-grid, but try to consume 100% of their solar generation. Sure, that’s great if you’ve got a smaller PV system and need to be really smart about your use.

I just don’t see the point in running a device you don’t need to for the sake of using up your solar power. Particularly when you can export it for the benefit of others (and yourself!)

The Good News

I think the concept of sonnenFlat is moving in the right direction in several key areas.

The surety for consumer electricity bills, while not demanding too much of their capacity to understand the system, is great.

The addition of more battery capacity in a VPP adds important ancillary services to the grid. This helps the grid evolve and integrate to these new, smarter services.


It also shifts the discussion about batteries further into the spotlight for the “Mum n Dad” consumer. While the Tesla Powerwall created a spark, it was priced only for early adopters. Powerwall 2 suddenly put the financials into reach.

This type of offering – promoting batteries as a service, not just a device – is an important step for consumer markets. One day, batteries and solar will not be a case of “are you getting one?” but more “which one are you getting?”.

The entire retail model is evolving, to the point where you’ll buy your battery and have a plug-n-play installation. Installing solar is slightly more difficult for the average home owner, of course, but it can happen.

IKEA are already offering shopfront retail in the UK, and it will only spread as retailers see profit in the full suite of service provision.

In the absence of anything resembling progressive Federal government policy, all these elements assist our systems to evolve.

More importantly, they help inform our consumers, who are also our electorate.

Year Of The Powerwall

Let’s get straight to it: 50 cents per day.

That is what I paid for electricity over the 350 days of billing I have since the Powerwall was installed, and my electricity provider changed over.

This is important to note, as the two weeks up to change of provider meant I wasn’t getting any export benefits from my solar panels. Mugged!

The saving is over the $2000 mark, but for the sake of round numbers, let’s call it $2000.

Year Of The Powerwall
OK, so not exactly this good, but pretty good…

To put in perspective what money means to my family: our recent road trip, to central and southern NSW, cost almost exactly that. Essentially, I got my little summer break for free.

Facts And Figures

According to the billing received by Diamond Energy over the 350 day period:

  • Import total was 1349.830kWh (or 3.857kWh / day)
  • Export total was 3807.403kWh (or 10.878kWh / day)

Not quite the 1:3 ratio I was looking for, but that figure is probably no longer simple to calculate, which I’ll explain below.

From the SolarEdge web portal, I have the following factoids:

  • Lifetime energy: 9.1MWh
  • CO2 emissions saved: ~3400kg
  • Equivalent trees planted: 11
  • Light bulbs powered for a day: ~26,200

That is kind of the feelgood stuff, despite the Powerwall not necessarily being “green” as people might imagine.

As with anything, there is a carbon cost associated with production. The early iterations of any battery product are going to be a little bit on the dirty side.

As one example: Lithium ore needs to be shipped from the mine to the refining facility. The refined lithium is then shipped to the cell production facility, which may or may not need shipping to the final place the Powerwall was built.

Tesla are addressing this with “vertical integration” of production, particularly for their cars, but also batteries in general. This means more processes can be done at one site, reducing shipping costs (and therefore carbon c0st) of transporting components.

Other Factors Considered

Keen observers will remember that in October I got more solar panels. That took my total system size to 6.5kW of panels. I just heard a bunch of critics trumpet “AHA!” but keep in mind, I still only have a 5kW inverter.

Therefore the maximum power I can generate is limited to 5kW, though the peak time lasts a bit longer on a sunny day.

It is hard to quantify what effect this has on the system, beyond saying “there is more solar capacity”. As the new panels are oriented WSW they’re not always going to be ruling the roost in terms of efficiency.

Its also a smaller factor than it otherwise would be, having been installed four months out of the year. Granted, they were the sunnier months.

Another consideration is my move to Time Of Use tariffs in the first week of August. This has an effect on two areas of my billing.

If I’m smart enough to “game” the tariffs, and avoid doing anything during peak time, I can save a lot. Unfortunately peak time coincides with oven and air conditioner use, so that’s not always possible.

The billing and the import numbers above will be affected by Reposit Power managing tariff arbitrage. When I import power now, it might be a result of my needs being bigger than the system output, the battery being empty, or because Reposit sees a cloudy day and wants to import some at a cheaper rate.

Putting together the new panels and move to TOU, a better time to revisit this might be October this year. That way, I’d have a true idea of what I can really save with all components working together.

The Vagaries Of Billing

Those out for a bargain will know to shop around with their electricity companies, and see how best to maximise their savings.

Whether that is through generous sign-up rebates, or big discounts for paying on time or via direct debit. It all adds up, and people without solar or batteries can benefit if they do their research.

As I pay such low amounts anyway, discounts don’t add up to much. Pay-on-time discount across the year was $20, and paying by Direct Debit discount was $17.62.

The bigger benefit was referring people on to Diamond Energy, which netted me $105 across the year. Against that, I paid $22 (inc GST) application fee with Diamond, so the benefit was more like $83.

If we add that $83 back onto the billing, it goes from 50 cents per day to 75 cents per day.

I pay about $1 a day to connect to the electricity network, so its still good. There are even a few dollars in GridCredits unaccounted for at this point.

Year Of The Powerwall

When I say “Year Of The Powerwall” I’m not speaking only to the year I’ve had. This year, 2017, marks the landing of Powerwall version 2 in Australia, and overseas.

I’ll level with you: I haven’t really spoken much about PW2 since the launch, because I’m still experiencing some angst.

Year Of The Powerwall
So hot right now…

I thought I’d done OK with my battery, then in the same year, Tesla brings out one TWICE as good.

C’mon Elon… I thought we were mates!

Overall though, this is a good thing. I think we’re about to see the domestic battery market kick off in 2017, with Tesla in front. That is quite amazing, given the prediction was market maturation in 2020. We’re three years ahead!

Talking to a few people getting quotes and installing them, right now there are very few people price-competitive per kWh.

As the manufacturers in Korea and China start their own uplift via vertical integration, prices are going to keep sliding, and competition increase.

This can only be a good thing for the consumer, for the grid, and for energy security and stability moving forward.

And any consumer who is getting a Powerwall 2: I think a zero electricity bill is well within reach.

If you factored in selling power back to the Grid out of the battery, which I think will replace solar feed-in tariffs eventually, you could even turn a small profit.

As always, user experience may vary. Its up to you to make the most out of your investment.

An Addendum

As I wrote earlier in the month, we have had some heat wave conditions here in Sydney, with outside temperatures getting into the high 40s (120oF). That was kind of insane, but it kicked off some GridCredits for me, which is also a good thing.

As we’re moving toward more extreme weather events, having a flexible and robust grid, with user storage available for emergencies, will be important.

Heatwave Conditions Do Not Compute

As we sit here in a rare Sydney heatwave, I decided to blog. Its all I have the energy for.

Temperatures today are predicted to reach 46oC today. That is 115oF for those of you with funny thermometers. Sydney is supposed to hit a record February day, in fact.

As the temperatures rise, the standard position for most people is to turn on their air conditioner and shut all the windows. And that is great; electricity can often be the most efficient way to cool space.

The problem is the load it puts on the grid, and the possibility of blackouts in many areas, as people ramp up power usage in heatwave conditions.

The kicker: Australia has more than enough generation capacity to cover its needs. This overcapacity is only useful when the market operates correctly though, as this video shows.

In a week where the Federal Government decided to use coal as a political football*, particularly on their support of coal over newer technologies, videos like this show how broken the system is.

* That is a really good article by Lenore Taylor above. Stop and read it. Give her a follow.

The good news is: consumers can help save it.

Combating the Heatwave

Normally you’d expect me to go on a rant here about Reposit Power and how microgrids are going to save the world.

The problem is that we’re continuing to consume high amounts of electricity to keep comfortable. If the heatwave conditions continue due to climate change, consuming even more won’t help – it will just make us hotter!

We’re stuck with fossil fuels for now, even while renewable technologies like solar, wind, and storage ramp up. In Australia at least, they’re going to be the majority of power sources until at 2025. Maybe longer.

As we’ve seen from The Guardian video above, the market can be “gamed” by generators, to help drive prices up. Even if you got a million Reposit Power boxes controlling 10MWh of storage, you’re not going to redress a balance of GIGA watts.

Part of the solution has to be a way to use less power. Therefore, instead of microgrids saving the world, I’m going to talk about something far simpler. Many countries in the world already practice it, but for many and varied reasons, Australia doesn’t.

Energy Efficiency

Its a topic that is not nearly as sexy as GridCredits, but in Australia, its probably more important than ever. Let’s start with a quick diagram:


While that is a gross simplification, the basic truth is there:

  1. Inefficient houses are built a lot here (and at high density)
  2. They need more power to keep themselves cool or warm
  3. This needs more power from (majority) fossil fuels
  4. That makes more profit for electricity companies*

* It should also be noted that it means more (moar) profits for home builders, because the materials for less-efficient houses are correspondingly cheaper.

Its a vicious cycle, and its particularly ridiculous in places like Sydney where land is expensive to buy but houses are cheap to build. And once they’re built, they grow in value (but not efficiency) almost overnight.

I understand this because I bought a house three years ago and watched it increase in price 25% in that time. And it isn’t any more efficient today than it was the day I got it.

Except the pool pump I replaced, but that is another (angry) story.

Consumers Will Consume

Nobody wants to spend any more money than they have to on building their home. I dig that.

I lived in a house with two reverse-cycle split A/C systems for years, and always wish I had ducted.

When I got my new house, it had ducted. And the electricity bills were much bigger. But I didn’t put all of that down to the A/C – it was part of the issue, sure, but I had a bigger house with a few more TVs. Yeah, that must be it.

Now that I have the data on what it costs to run, I’m appalled, and looking for alternatives.

The first part was solar PV and a battery system. That has helped slice my electricity bill into tiny little pieces (blog coming soon on that).

To take it to the next step, I’m going to look at making my house more efficient. As I wrote back in March 2016, there are weak points in my house that need looking at.

Those windows on the west side of the house are next on the list, and I’m getting quotes for double-glazing and glass film technologies as we speak.

Advice For The Home Builder

If you’re building a home at the moment – or even renovating – I’ve got some advice for you, on how you can help with this heatwave situation. This covers both your personal comfort levels, and your contribution to the environment.

Look into designing your house right. Make sure you’ve got decent eaves. Windows that aren’t monstrously oversized. Understand the quality of the wall and ceiling insulation and MAKE SURE it covers the garage; many builders don’t insulate the garage, so its a massive heat collector, and can radiate through internal walls.

DOUBLE-GLAZING. Adds to the initial cost of construction, but will reduce your energy costs by 25-50% depending on aspect.

Get the Air Conditioner you NEED. Don’t just get the biggest one or look at the cheapest price. With the weather warming in Australia, you need to be sure that your A/C is smart. Make sure it is an inverter, and don’t worry about the slightly higher initial cost. It will pay for itself in efficiency measures, while electricity prices continue to rise.

If you find its not enough, then installing a small split system in a particularly bad area of the house can be done later. If you buy the big unit, you’re stuck with it for good.



Also, don’t be that guy who sets it to 21C appropriate. Your house should never really need to go below about 25C to stay comfortable if the thermostat is set up correctly, in the right location. This will save you thousands in electricity costs over the lifetime of the system.

Use ceiling fans and portable fans tactically, to keep air moving around your house. This is also part of using the 25C rule. If the air is moving, it often feels cooler, and the cost to run one is minimal.

Politically Speaking

The last measure you can do is speak to your local member about raising building efficiency standards in Australia.

I was fortunate enough to hear Dr Brian Motherway talk about efficiency at a conference last year. Efficiency is one of the key targets of the International Energy Agency.

Countries like China are ramping up policy and action in this area, as well as decreasing their reliance on fossil fuels in favour of renewables.

Those nations that don’t look at the entire energy spectrum are going to be left behind. And what is the point of pursuing a green grid if we’re still wasting it?

With that thought foremost in my mind, I’m going to jump in the pool with a beer.

First Anniversary of Powerwall

This week I’ll be celebrating the First Anniversary of the Powerwall’s installation at my house. How time flies!

I’ve been on holiday for a few weeks over summer, and what a summer it has been. In two words: bloody hot.

Sydney has been experiencing some of its warmest weather on record, with temperatures hitting up to 45oC (113oF) and not cooling down below 30oC over night. Distinctly uncomfortable.

So you end up with successions of hot days, but worse: hot nights.

At least it wasn’t peak pricing that day, being a weekend… Small mercies.

In addition to the anniversary, I’m also due to receive a bill from Diamond Energy, which will cover November through to January.

Putting in a guess right now: I’m going to say about $1.20 a day, excluding referrals. Similar to Winter, but with a bit of a discount for better export. That would be a bill of around $110 for the 92 day period.

Changing Seasons

Summer has definitely had an affect on the system, in terms of import requirements. As I mused back in December, summer would require more import, despite having more sunshine to work with.

Part of the reason is electricity consumption; on the whole, I am using more energy due to cooling and things like the pool pump.

The air conditioner is variable, depending on ambient temperature, and required comfort level. Short of replacing the thing, I’m stuck with needing the grid during summer.

The pool pump is fairly static in terms of use. A set number of hours per day, and roughly 1kW consumption, makes it easy to calculate.

How you handle your pool pump usage is up to individual circumstance. My pump has a flow rating of approximately 19,000 Litres per hour, and a pool of 31,000L capacity. I have a cover on it all winter, except for monthly maintenance, and no trees or other debris issues around the pool itself.

Therefore, in winter I’ll run it for around 90 minutes per day which should turn the capacity over about once. With appropriate chemical balancing, that keeps it clean.

In summer, I’ll vary it a little. During summer peak – where we use it a lot – the run will be 6 hours, timed for peak sun. At shoulder times I’ll start to move toward 4 hours, as we’re not using it as much.

The idea is to let the filter work as hard as it needs to, while retaining good chemistry and clarity in the pool.

Capacity and Usability

Happy to report that the Powerwall is still reporting its full 6.4kWh capacity, same as Day 1 of the system.

The extreme heat over summer also didn’t trouble the liquid-cooled unit. The Powerwall is rated to 50oC, unlike many of its competitors, so even an Australian summer can’t dent it.

Unless you’re crazy enough to put the thing outside. In the sun.

Businessman Laptop Desert
“Gee, the PC fan is really working overtime today…”

What I did notice was the rest of the system struggling to get to full capacity. With a total of 6.5kW of panels on the house, I didn’t always reach the 5kW capacity of the inverter.

Part of that is the panels getting hotter than their efficiency peak of 250C, and part of it is the inverter starting to feel a bit of heat stroke. Even in the shade, on the south side of my house, it gets bleeping warm.

Back in October I was hitting some sweet numbers, but the ambient temperatures were down in that 25 degree range. Everything performs better when its cool.

Post-Anniversary Focus

As the year has worn on, I’ve slowly weaned myself off frantic chart analysis. Its a bit of a pragmatic move, as constantly worrying about my ROI was a bit stressful.

While it was important to keep an eye on the system, I’m moving into a stage where I need to look at the future path, not just the past performance.

That means I’ll be presenting more ideas-based blog here, and there is plenty to write about.

Tesla Energy released the Powerwall 2, which I’ve avoided talking about due to extreme jealousy and consumer cognitive dissonance.

Accompanying that is solar rooftop, which I’ll talk about in a future post.

World-shaping events like Brexit and the election of Donald Trump are key political events. They have the potential to shape energy policy for years to come.

There are also ideas I’d like to explore in terms of other energy sources. That will lead into producing educational content that I can distribute, through various media.

I’m also aiming to put up more on my YouTube channel, for which I’d appreciate a “Subscribe” if you’re so inclined. Which I’ll try to fit in around the blog itself, work, family, and running a Rugby Club!

It has been a very interesting journey to get here. It wouldn’t be possible without the generosity of time and patience of the following organisations:

Natural Solar


neonblackSolar Edge Logo


Recalculating Payback Time

As mentioned in October, I got some new panels, so I thought I’d have a quick run at recalculating payback time.

No doubt the new, west-facing panels, are having a positive effect on electricity generation. As the days get longer in Summer, clear days are cranking out 2-3 times as much as the house consumes!

Of course, its not all gravy, with this last week in December producing two extremely hot days above 36oC (~97oF), followed by two days of rain. The former item consumed a lot of air conditioning, while the latter didn’t generate a lot of PV energy.

I’d love to have a Powerwall 2 to ride all that out! But I make do with having a grid connection.

Payback Parameters

The new panels were $1320 including GST. That takes the total system cost to about $18k at this stage, now including 6.5kW of PV, inverter, Powerwall, and Reposit.

That is an increase of roughly 8% over the original cost.

Generation capacity has increased by 1.5kW / 5kW = 30%.

That figure is a bit fuzzy because the existing panels don’t face the same direction as the recent additions. Also, the inverter I have is limited to 5kW of throughput. So chances are I won’t use all of that capacity across the year. Let’s call it 20% as a “real” figure.

Regardless, the main point is looking at the cost increase over the capacity increase. Extra funding of 8% has allowed my system to gear up by a potential 20-30% in terms of generation.

This shows what anyone experienced with solar will tell you: panels are cheap. Get as many as you can, with the biggest inverter possible.

As I mentioned in my last blog post, I now have data on finalised billing to cover about 70% of the year.

It shows my electricity cost – including daily connection fees – at roughly 71 cents per day.

Summer is yet to be added to this data set. Like winter, the primary environmental control (my ducted air conditioner) will get usage. I also have a pool pump that runs more in summer than winter.

Looking at historical bills, I tend to use about 3% more in Summer than Winter. Whether that still holds true depends on a lot of factors, particularly seasonal variance. Maybe we had a warm winter last year? I can’t remember.

This may not be significant in the face of increased solar generation:

  • Self-consumption can increase with longer daylight hours
  • Export can increase with higher generation capacity


Taking a Stab At It

Alright, so putting my analytical neck on a chopping block, here is what I think will happen.

Disclaimer: I am cheating a little in that I have data from Reposit Power to guide me on the days I know about since the last bill. To balance that out, not all my billing days were time-of-use (was on single-rate until August), so I’m flying blind in other ways.

As I’m writing this, I have realised just how many moving parts there are! This is going to be tricky, so let’s start with actual data.

Looking at the Statistics page of the site, fed by SolarEdge API, I can see my lifetime system statistics. All of which is very interesting to look at, but only two matter; import versus export.

Summary Import and Export – second week of December, 2016

These two factors are Summer in a nutshell. Increased import, possible reduced export. The daily average covers each day in the last week (up to 16th December, inclusive).

If we add the 3% increase I am predicting for summer from my historical billing, it doesn’t change the import much. The lifetime import has only been around 3kWh per day, so 5.47kWh per day represents an increase of 2.5kWh.

With peak tariff, this could be as high as 90 cents per day! Shoulder rate and offpeak rate make it 69 cents and 35 cents respectively.

I also need to factor in that Reposit Power imported a few offpeak kWh on Friday morning, so will call the extra import 2kWh per day. I’ll use the peak tariff rate to established increased costs of 75 cents per day.

On the flipside, I don’t think the 9kWh export figure is accurate due to the amount of cloud we had over the two days. The lifetime average is about 11kWh. To this, we add the 20% of our extra generation capacity to arrive at 13kWh per day.

“Wait a second!”, I hear you cry, “you’ve already had those extra panels on for a couple of months!”

Yes, I agree. However, we’re now hitting peak summer, so given my 20% figure was a fuzzy projection, based on 30% increase in capacity being the limit, I think it still works.

Again, looking at the statistics, you can see the 28-day retrospective is 13.92kWh. So I’m sticking with about 13kWh per day, keeping in mind I’ll be self-consuming a bit more than usual with the pool pump running.

An extra 2kWh per day exported is 16 cents in reduced costs.

Combine the two of those, and we had 75 – 16 = 59 cents per day.

This is extra, over the historical average of 71 cents per day. This brings us up to $1.30 per day for the summer bill.

Remember, I proposed a 3% increase of Summer over Winter, based on historical billing. The “Winter” bill I received back in September was $1.27 per day.

If you add 3% to that, you come out at $1.31 per day, so I’ll be keen to see if I get that close to my estimate of $1.30.

But What About Payback Time?

Very good question. I’ve just added $1320 capital cost to the system, and spent the last couple of hundred words speaking about Summer only.

Using the summer figure I calculated above, and wrapping that up into the billing I’ve received, puts the annual cost of electricity at my house around $310 as I’ve stated previously.

That is a saving of roughly $2k per annum over my old billing from last year. With the system cost now at $18k, that is a 9 year payback on simple calculations.

However, Autumn and Spring are the counterpoint to the Summer and Winter electricity burn for cooling/heating. Those times of year need to be exploited.

If my exports climb by 20% for both those seasonal bills, then the gains per year could be quite gratifying.

The two bills I have for these periods work out to 59 cents per day (March-June using single-rate tariff), and 24 cents per day (August-October on time-of-use).

The other key factor was full operation of Reposit Power with TOU tariffs, with is another massive advantage along with GridCredits. I can import very cheap power for anticipated poor days of PV generation.

Along with the extra generation capacity of my new panels, this shunted the power per day figure down by nearly 60% for Spring over Autumn.

If this holds for next year, and the Autumn power bill goes down to under 25 cents per day, it will mean for half the year I’m paying $44 for electricity. For the other half (Summer and Winter) I might be paying about $240.

An annual power bill of $282 sounds a lot better than the $2300 I was paying a year ago. And shifts simple payback under 9 years, by a few months.

The addition of these panels doesn’t look like a big deal on the face of it, but I’ve been fairly conservative in a lot of estimates.

I haven’t taken into account any GridCredits I receive, or the Diamond Energy Customer Referral fees I might get. So perhaps under 8 years is possible once the whole-of-environment changes are considered.

Christmas 2016

I’d like to thank everyone who has popped in for a look at the blog this year. Thanks for the connections on Twitter as well!

It has been quite an interesting 11 months since I got the Powerwall installed, and I’ve certainly learned a lot.

I have made an effort the last few years to put up Christmas lights, and copped sunburn, cuts and scrapes doing it. But its definitely worth it for the look on the faces of the local children.

I would like to wish you and your families a safe and happy holiday season, wherever you are.

Agile Energy Projects in the Marketplace

It has been a hectic couple of weeks, after the release of my first quarterly power bill. I’ve been on radio, TV, in print, and sprayed around the internet. Its a bit like the install day back in January, but obviously with a dollar figure attached.

Despite that, there is still a lot of people ready to step up and put the boot into Powerwall, and lithium storage in general. I will never fathom why these parties are against progress, so I don’t read into it too much.


During that time the world rolled on, and it appears renewable energy, particularly solar hybrid, has been going from strength to strength. One tweet in particular caught my eye, from Noah Smith.

The Telegraph article linked by that tweet, written by Ambrose Evans-Pritchard, is an interesting discussion on battery storage as it affects the landscape. It is also a bit of a dig at the Hinkley Point nuclear project in England.

I wrote something previously on Nuclear Power, so without a re-hash I will reiterate: I AM NOT ANTI-NUCLEAR. However, I did point out there are significant financial hurdles to overcome in Australia. Leaving aside the social issues, that is.

Three paragraphs in the article from Evans-Pritchard got me thinking.

Perhaps the Hinkley project still made sense in 2013 before the collapse in global energy prices and before the latest leap forward in renewable technology. It is madness today.

The latest report by the National Audit Office shows that the estimated subsidy for these two reactors has already jumped from £6bn to near £30bn. Hinkley Point locks Britain into a strike price of £92.50 per megawatt hour – adjusted for inflation, already £97 – and that is guaranteed for 35 years.

That is double the current market price of electricity. The NAO’s figures show that solar will be nearer £60 per megawatt hour by 2025. Dong Energy has already agreed to an offshore wind contract in Holland at less than £75.

Those are some pretty compelling numbers, but the reasons why it got me thinking relate to my own work life.

A Short History Of Dwarves

I’ve been an IT guy for a living nearly 20 years now, working mainly in databases where I can help it. I’ve seen almost every tech acronym or buzzword put into practice, sometimes very poorly. Or for the sake of change.

One of the better periods was back in the day, when the technical stuff was held apart. I like the imagery that Neal Stephenson uses in Cryptonomicon – IT guys were like the Dwarves in Tolkein; working away in the dark, hammering out things of beauty like Rings of Power.

The company (Elves) would frolic up to the entrance of the forge, beseeching the Dwarves for a solution. The Dwarves would give a range of timelines and costs, and the Elves would pick one. We’d go into the forge, create what they wanted, and the land was content.

With advances in technology, and the hunger for globalisation, things needed to move faster. Thus, “Agile” was born as the new way to do things.

Dilbert official site "Agile" search - click for more...

Generally speaking, the move to Agile is positive from my point of view. It seeks to guide the Good Ship Project through the icebergs as each one appears, not assert a course from Day 1 and expect no issues with implementation at all.

As long as Agile is implemented the right way, it can do good things.

There is a caveat though, and the seed of this started with smart devices in my opinion. If we’re ever having a beer, talking shop, I’d pinpoint smart devices as disruptive in more than just a good way.

Now non-technical people see an awesome app for $1.99 and wonder why projects still cost millions. As a result, they demand more.

Agile has collided with this belief that speed of delivery, and convenience, is cheap. Non-technical people don’t necessarily understand the systems. They’re trying to tell the developer how to do their job down to the finest detail. That isn’t actually helpful.

Dear Managers: right now, there IT guys reading this, and nodding their heads. Maybe muttering. Likely, swear words and dark thoughts are being countenanced.

Agile Energy Projects

One thing that holds true of IT projects, energy infrastructure, and pretty much anything down to a backyard deck, is the Quality Triangle.

Time vs Cost vs Scope as it affects Quality

If you are going to implement or change the project in terms of finances, timeline, or scope/size, then you have to accept it will affect the quality of the outcome. Aiming for all three is purely theoretical, in my opinion.

As with the recent Census Fail incident in Australia, sometimes it doesn’t matter how many resources you throw at a project, or how long it runs. The excreta hits the rotary ventilator, and its time to put out fires.

Hinkley Point C is subject to some base requirements, but the main one is the generation of 3200 MWe from a nuclear reactor. Not the biggest in the world but still a mighty undertaking.

Once you’ve decided it will generate that much, you’ve set your course. A prescribed amount of effort, human resources, and other elements must go into it. Critically, the reactors will be of a certain size and type, and you’ll pay the capital cost of that regardless.

If you encounter cost overruns or other issues, generally speaking you just have to suck it up, as per the article:

… the estimated subsidy for these two reactors has already jumped from £6bn to near £30bn. Hinkley Point locks Britain into a strike price of £92.50 per megawatt hour – adjusted for inflation, already £97 – and that is guaranteed for 35 years.

In Australian terms, that is $160 / MWh, which is frankly ridiculous.

All of this points to the fault lines emerging in “baseload” power argument. Not only is “base” power a myth, but the agility of these big power generation units is practically nonexistent from conception through to decommission.

As Hinkley Point C, and Finland’s Olkiluoto construction debacles show, centralised nuclear power might be green, but it isn’t necessarily going to stand the test of time, economically.

Smart Advantage of Renewables

Technologies I have seen work, or worked with directly (like Reposit Power) show us that agility is the biggest factor in any tech marketplace today.

And let’s not kid ourselves: energy delivery is now a technology field. This is particularly true of renewable energy, which eschews the old school sledgehammer approach to power generation, in favour of smarts.

Smart use of power, smart direction of power, are going to be the big players moving forward. It starts with domestic applications, such as Tesla Powerwall, and smart management to deliver benefits for the home owner.

Beyond serving one household, it has the potential (and in some ways, the obligation), to serve the wider community.

This is achieved by using the battery as a trading platform. Benefits abound for the network willing to engage with customers, as I discussed in May. Reduced overall costs and waste benefit everyone in the longer term.

This move toward smarter storage also helps address the business sector. The power needs there are large, and despite being mainly during the day, will not going to tolerate the intermittent fluctuations of solar PV and wind.

Storage using batteries is one leg of the argument, across a various range of chemical makeups. Energy storage like pumped hydro can also assist deliver stable power on a larger scale. The big one for Australia should probably be molten salt reactors, particularly for South Australia, which has suffered issues recently.

Certain industries have scope for change today. Heavy transport, and transport in general, is already under the microscope in nations like Sweden, where they seek further reduction in carbon emissions.

Electric Vehicles take carbon off our roads and out of the manufacturing process through a simpler template of construction. If you don’t believe that, think about the amount of metal required to build a drive train for a petrol engine, versus an EV’s battery & motors setup.

How do we address the remaining heavy industry players, and areas outside domestic power supply that aren’t easily converted to renewable technologies?

Scale Advantage of Renewables

Critics of renewable energy sources often derisively quote land area required for building large-scale generation. Regardless of whether its wind, solar PV, pumped hydro, molten salt, or another method, a “farm” for renewable power will take space, that is true.

Solar Sunwerx 6 Florence Street BURWOOD VIC 3125
Nyngan Solar farm, Australia. Credit: Solar Sunwerx

Renewable energy projects are much simpler to implement from an engineering point of view, compared to a nuclear reactor. They are also more flexible.

A nuclear plant, once scoped, has very little opportunity for changing the Quality Triangle. It also isn’t going to get much more efficient if you delay implementation, because the technology is largely static.

Manufacturing issue with your solar PV arrays? Let’s just get less panels for now. They’ll be cheaper later on, or more efficient, anyway.

Dispute over one of your wind turbines? Fine: proceed with the rest of the farm until the outcome is known.

These are two examples (there are more) where the scalability of renewable energy creates a huge advantage. The unit size of a wind turbine, or a solar array, is in no way limiting for people who know how to implement them.

Concentrating Solar Power for an MSR (Molten Salt Reactor)

Pumped hydro and molten salt reactors are similar to traditional power stations, in that their capacity is roughly determined at time of construction. The key difference is they are primarily storage, over and above being generation.

They don’t need to be on all the time, only engaged when other resources are running low, or as demand spikes. This is another advantage over “baseload” coal or nuclear, which cannot uplift to address demand spiking.

Only gas-fired stations have this ability at the moment. The surging price for gas, as well as its status as a fossil fuel, renders it a short-term option at best.

The Paradigm Shift

You cannot simply build a traditional network and throw more and more renewables at it until you reach a very high number.

Coal in Australia has been built to over-capacity, resulting in wasted capital expenditure, and poorly managed outcomes. Witness the issues South Australia has at the moment, because of short-term thinking around renewable energy integration.

We need “smart” implementation of renewable energy projects. Flexibility must remain a core tenet of implementing this intelligence.

As Evans-Pritchard covers in his article, there are many storage options in development across the world right now. We’re in a period of real transition where more options will blow the marketplace right open.

This requires the right thinking, to engage renewable sources on a far larger scale, holding hands with storage options of all kinds. Markets will shift rapidly. Consumer needs, particularly in the developing world, will have no need, and no money, for sledgehammer tactics like “baseload” power.

Projects designed for even 30-year life cycles will find themselves at risk of rejection. It will be simply uneconomical to support such inflexible systems.

With the right people at the wheel, concerns over our energy needs, and the perceived shortcomings of renewable energy, needn’t be a concern.

Billing Awesomeness Powerwall Style

As I’ve been hinting for a while, the first bill has landed – Billing Awesomeness Powerwall Style! The guys at Natural Solar and I have been jumping out of our skins to get this moving, but all good things in time.

Natural Solar

I’d better come clean – technically this isn’t the “first” bill. I actually got one over a month ago, which only covered 35 days due to various scheduling issues with the meter changeover and reading.

And don’t get me wrong: that 35 days was a very small amount, particularly as my last summer bill was $660 (!!!), but I felt it best to wait and see.

Now that we have a quarterly amount, which also lines up roughly with the same billing period last year, I (and everyone watching) can compare apples more easily to apples.

Let’s go to the numbers, courtesy of my poor quality photography. Here is the bill from the “Autumn” quarter last year:


Of course, I’m a fine and upstanding citizen (stop giggling), so I paid on time to get the appropriate discount under my plan.

And here is the bill from “Autumn” quarter this year – this amount also includes the pay-on-time and direct debit discounts:

Billing Awesomeness Powerwall Style

Ninety per-freaking-cent reduction!

Not too shabby, but as always, it isn’t the whole story.

The 2015 bill overlaps the 2016 period by a few days at each end, so this is only a fair comparison if we look at the number of days on each bill. Hey let’s do that to FOUR decimal places!

Year Days Cost $ / Day
2015 99 $490.38 $4.9533
2016 86 $50.39 $0.5859

So… yeah… that’s 59 cents per day for electricity. And if you recall my ROI/payback article from April, you’ll know that under Diamond Energy single rate plan I pay a tick over 82 cents per day for connection, so I’ve even reduced the connection fee by a fair whack.

That makes it pretty clear that I was smashing out the solar power with extreme prejudice from my 5kW array. The final number was a tick over 3 kWh exported for every 1 imported. Always going to look good when you’re getting 8 cents for export, from the legends at Diamond Energy.

I will throw in here: that bill doesn’t contain a single GridCredit sale, either. Nor does it contain any off-peak (TOU) power. That is pure, single-rate, import versus export.

And I think I could do better, but we’ll get to why that is later.

Billing Awesomeness Powerwall Style – Factors

I suppose it was a pretty mild weather period, but then in Sydney for the Autumn period that’s not unexpected.

Looking at the energy consumed per day is also helpful:

Year Days kWh consumed kWh / Day
2015 99 1777 17.9495
2016 86 1180 13.7209

Note that because I don’t see how much I consume on the bill, I’m having to use the data generated by the SolarEdge API. In my experience so far it is fairly accurate, though it has a small degree of variance due to updating on the quarter-hour, as I understand it.

A good reduction in usage, due in part to having a couple of new devices we needed to replace, like the oven. The old one was listing badly to port, in naval terms.

That reduction is also about learning my consumption patterns via the SolarEdge and Reposit Power portals, and coming up with the best way to eliminate waste.

I’m also paying a bit less for my power overall since changing providers, but as I’m only importing around 3kWh per day, that is of negligible effect on terms of cents per day. The connection fee is only a tiny percentage different.

Critics will be quick to jump in at this point, with smugness, clamouring that its NOT just the Powerwall.

While that is a fair point, at the same time, they should not be dismissive of the lessons the system has taught me.

To digress into simile for a moment: I went to University, and it cost me a lot of money, but it didn’t get me a job; it gave me a mindset, problem solving skills, and the experience of those who were my educators.

Likewise, I have not just purchased a battery, but an entire solar PV system with smarts. With it, I have been given the opportunity to generate, store, and export that energy. I can access new energy trading markets such as GridCredits.

Most importantly, I have a new way of thinking, evidence to track my progress, and help from a range of people across the industries involved.

The battery, by itself, doesn’t deliver miracles, not was it ever intended to. I’ve made it very clear from early on that there were tangible benefits to the Powerwall.

The power shifting aspect of the battery is extremely important to reducing my import requirements. I don’t get Gross Tariffs, so moving what I can to the daytime is great.

BUT we don’t get to spend our whole day at home (the kids would drive me up the wall), so there needs to be other ways to reduce or offset that cost. That’s where the Powerwall takes over.


The ROI blogs I’ve written state quite clearly that any household could save money by making simple changes. Smarter devices. Better practices. Maybe a new billing provider. It didn’t matter whether they had even had solar PV, much less a battery.

A household with Solar PV on Net Tariffs has probably learned some of these lessons already. For them, the cost of a battery is a marginal prospect today but is certainly on the radar.

A household with Solar PV and Gross Tariffs in NSW is probably looking for “what next” as they lose those benefits at the end of the year. Perhaps they haven’t had to think about these factors, but they probably will (and I know some who are), once they start actually importing power at a cost ratio which reverses Gross Tariff costs.

I just look at the FACTS: I’m saving about 90% on my power bills. I’m making my household greener than it was, through waste reduction and buying green power. I’ve been asked to relate my experiences at conferences, schools, and work places.

People are interested in this technology, and want to see it in action before they commit. Hopefully this kind of real-world data, even if its only one site, will help.

As a side note, based on this one bill, the return is in the order of 10%. Extrapolating that, factoring degradation versus increase in power costs, the 10 year window on my warranty is looking pretty safe.

And I’m not done.

The next arrow out of the quiver is my upcoming move to time-of-use
billing. That way, I can start really getting the most out of the Reposit Power software to drive those costs down even further.

Energy Networks
This lighting really makes me look good…

Billing Awesomeness Powerwall Style, away!

Test Driving the Model S

Today I had a crack at driving the Model S. This was a favour teed up for me by the good people at Reposit Power. They used it as a bit of a thank you for my help at that conference back in May.

I’ll level with you: there is no way I could afford even a base Model S.

In Australia the absolute base standard model is over $110K. That includes all discounts and incentives – of which, thanks to our backwards government, there are few.

I drive a Nissan X-Trail (the last of the “boxy” X-Trails from 2012). The wife has a Yaris. So we’re not “rich car” people. Even the base Model S is about 3 times the cost of the most expensive car I’ve ever owned.

However, in good news, today’s test drive was not in the base Model S.

I was in a dual-motor Model S 90.


I have been thinking about owning an EV for a long time now, and about how it would feel, and how it would respond.


I was unprepared for the sheer awesomeness of this event. The lightness of the steering, the road responsiveness, and that is without me even thinking about the tech that underpins the whole thing. Sure, I’m not a luxury car drive ordinarily, but MAN!

We spent a bit of time driving around Sydney’s lower north shore, getting a feel for the capabilities and luxury of the beast. And the silence, which I found a little unnerving at first, but quickly learned to laugh at… somewhat deliriously.

What I hadn’t appreciated previously, when freaking out about the Model S, was the simplistic elegance of the design. Besides the main screen with all its configuration (handled wonderfully by Adele from Tesla, guiding us on our magical space journey), everything is really thoughtfully laid out and simple to operate.

You just get in, and drive, and nothing about it is an issue, even for a first-timer. Well, except the left-side indicator stem… European layout… Hmph. I’m just used to Japanese cars so no biggie.

We experimented a little with the different modes, and it was really amazing how quickly the car shifted to Sports and Performance modes. You could feel the suspension and steering sharpen up as soon as Adele switched it over, even at 60 km/h.

We also drove past an Audi R8, and we all had a good laugh at the difference in price versus performance.

The Autopilot was really cool at notifying cars and other objects that were within the car’s sphere of influence. It was really noticeable how different the layout was to other cars I’ve driven, particularly the space down the middle of the vehicle, and smart use of every area.

And then, there is that acceleration… I’ll let this short video (and my daughter) do the talking…

We also had a poke around the showroom, looking at the cars and bare chassis, as well as the Roadster they had on display.

IMG_20160723_123954 - Copy IMG_20160723_124043 - Copy

I am also proud to say that I have now added a second Tesla to my fleet.

The Winter Of Our Discontent

Now is the winter of our discontent
Made glorious summer by this sun of York;
And all the clouds that lour’d upon our house
In the deep bosom of the ocean buried.

– Gloucester, Richard III (William Shakespeare)

OK so perhaps I’m using that a bit out of context; where Glouceser is speaking on a time of unhappiness past, I’m in the middle of winter, and I’m fairly discontent!

Mainly because it is one of the coldest winters in Sydney for about 20 years so far, with some record days in terms of low temperatures. I’m not even going to type that much because a warm bed is calling me.

Frost isn’t unusual for Sydney, of course, particularly in the western suburbs. But it has hit a little earlier than I remember, and daytime temperatures are staying in the mid-teens, or around 60oF.

This is Australia for goodness’ sake! We don’t DO cold.

That attitude is reflected in our lack of double glazing for standard housing. If I had the money, I’d give it some serious thought.

What it has meant for the UTP household is an increase in imported power as we run that (cursed) ducted air conditioner for heat.

Here are some of the dials, edited to exclude GridCredits/Battery, from Reposit Grid Portal, Wednesday 29 June.

winter discontent

This is the general pattern on a bright winter’s day – we get up and consume a whack of energy in the morning, with the ducted heating adding to the breakfast needs. The green spikes on the top right are around 5kW consumption, mostly import.

The Powerwall is typically exhausted by morning in this weather, due to evening heating requirements. This is utterly necessary to prevent widespread misery, wailing, and gnashing of teeth.

I’m not even complaining about the heater usage because brass monkeys are getting distinctly uncomfortable. Its that cold.


Get the ice scraper, Edgar… and the thermals…

You can see from the Reposit data screenshot that the solar generation is still kicking a fair amount of butt on the bright days, with the light hitting the panels from around 0730 hours through to around 1630 hours here. It’ll get up to around 3.8kW in the middle of the day.

That is a fairly good amount of power considering we’re in the shorter daylight period of the year. A week earlier, right around the equinox, I did 21.5kWh which is pretty schmick. Either side of that, it was closer to 12.5kWh as intermittent cloud interrupted my flow.

I’m even exporting a few kWh because the battery is still filling up before midday. On cloudy days, I’ll turn the pool equipment off to save about 1.5kWh of electricity as well. So while its not all gravy, its still cheaper than having no solar/Powerwall at all!

Its just addressing those morning and evening heater requirements that is the issue, and even with the thermostat set to 19oC, there is a fair bit of juice needed to kick the old girl off.

I’m getting a meter changeover done so that I can move to time-of-use. This will take full advantage of Reposit’s ability to charge the battery off-peak and deploy that power when I need to head off peak running.

Speaking of which – first bill due in the next week, so expect excitement!

Model S Freakout

Was working from home today when the wife asked if I wanted to join her for lunch at a nearby shopping centre. It helped that she sent me a shot of a Tesla Model S on display.

Before the phone hit the ground…

Road Runner
That’s me in the distance….

Arriving out of breath, perhaps having broken several land speed records, I got a glimpse of it, and it was a P90D! Not the first Tesla I’ve seen in the wild, but definitely the first stationary one I’ve been this close to.

Model S

I took the time to walk around the car, introduce myself to the Tesla staff on hand, announcing my status as a Powerwall owner. They were excited to meet me, but not nearly as excited as I was just to be near it.

Model S

After examining it from all angles, I eased myself into the sweet, sweet luxury of The Magical Space Car for the first time.

Model S

Oh man… if I was a smoker, I’d suggest a cigarette was in order…

I make no apologies for any spelling mistakes or grammatical errors here, BTW. I’m too excited to care.

I played with the massive touch screen for a little while, pressed all the buttons, and also took time to check the back seat for room.

Only thing I’d have to criticise is the rear head room was a bit tight if I sat up dead straight and tipped my head back. No complaints about seat comfort though. And that body work… mmmmmm…

Model S

This model had a few upgrades that one can’t experience while it is immobile in a shopping centre. The base model shares a lot of the same interior features of course. Just a shame even at basic RRP here in Australia (starting around AUD$130K), it will remain out of my price range.

But it was great just to hang around for 10 minutes and discuss the car, the opportunities, the upcoming Model 3, and charging infrastructure.

I also got in a quick plug for this site, as well as people like Matt, who has driven his Model S from Perth to Sydney, and will continue on to Brisbane.

He’s practically the Silver Surfer, but using a car instead of a surf board.

After about 15 minutes of geeking out, talking to the Tesla staff, and answering questions for other customers when things got busy, I sadly had to leave.

I was going to put a deposit down for a Model 3 at launch, to replace my wife’s car. Around the same time, she picked up a job with a car as part of the package so that plan went on the back burner.

I figured, since it was a Ford Fiesta with a very efficient engine, it was at least part way to the green aspiration I have of an electric vehicle.

One day, Elon… one day…