Springtime for Positive Billing

As per my tweet earlier in the month, the new bill came in, and it is really  the definition of positive billing.

It is the first bill I’ve received with TOU (Time Of Use) tariffs, which changes the landscape a bit for me.

I already have data from Reposit Power about billing estimates on a daily basis. While they’re pretty sharp, the guys doing the billing are where it counts. I wanted to see how close all the estimates – including my own – would be to the truth.

The net result is a deposit into my bank account (yesterday) of $50.25.

Positive Billing Spring
Billing Summary November 2016

The Breakdown

The fixed costs were as follows, excluding GST, for the 84-day period.

Item Quantity Price Amount
Service connection fee 84 days 98.90 c/day $83.08

Usage over the period at the various TOU rates came to the following (all amounts are excluding GST).

Item Qty (kWh) Price (c/kWh) Amount
Peak –¬†Rate 1* 24.962 30.5300 $ 7.62
Peak – Balance 0.000 31.4900 $ 0.00
Shoulder Rate 76.635 24.9700 $19.14
Off Peak 74.584 13.8400 $10.32

* This covers the first 340kWh / month

I imported only 176.181kWh over an 84-day period. That works out to just under 2.1kWh per day during that time. Only 0.3kWh in peak tariff period!

There were a couple of rainy days in a row that I recall. One of those coincided with hosting a family event, using the oven, and dishwasher a couple of times. As it was the weekend, shoulder rate tariff applied.

Factors in my favour are summarised in the table below.

Item Qty Price Amount
Net feed-in tariff -1099.299 kWh 8 c/kWh -$87.94
GridCredits -5.04 kWh 100 c/kWh -$ 5.04
Renewable Reward 84 days -8.710 c/day -$ 7.32
Direct Debit Discount 3.0 % -$ 3.60
Pay on Time Discount* 7.0 % -$ 6.75
Diamond Referral  2 -$35.00 -$70.00

* This amount is calculated against the previous bill

The export figure is massive at nearly 13.1 kWh per day! Its worth noting that the new panels I got in October covered about 25 of the 84 days in this billing cycle.

The first lot of GridCredits were applied to this bill, and that $5.04 is handy for knocking the top off that peak tariff.

Once you throw everything into a pile, and calculate GST, you get the balance of -$50.25. Diamond will credit your account for any amount of $50 or more owed. For the first time ever I have positive billing for electricity in my favour!

About those referrals…

Yes, Diamond have a pretty generous referral scheme. Both the existing customer and new customer get a $35 credit which is pretty sweet. Long may it continue!

Having just one of those per quarter could help the electricity bill head drastically toward zero. The question is, how many friends and family can you tap into on a regular basis? ūüôā

Let’s remove¬†that $70 amount from the¬†equation to look at the¬†regular money.

Just The Facts, Ma’am

You know the deal...
You know the deal…

We now have an electricity bill of $19.75, or 23.5 cents per day, which is even lower than my first full bill in July.

When you export enough energy to cover your¬†service connection fee, you’re doing pretty well.

When you self-consume most of the rest, and only bring in a very small amount of peak power, that is obviously much better.

The Powerwall is essential to this plan, because it avoids peak tariffs using Reposit Power for tariff arbitrage.

That said, summer reality is starting to hit. As I write this, the outside temperature is creeping up toward 37oC (99oF). The air conditioner is running. Cloud cover is building as we head into the afternoon, and peak power tariff kicks in.

I’m taking this opportunity to experiment with the ducted air conditioner. I need to determine how to minimise cost without unduly affecting comfort levels.

Billing cycles will now fall roughly into quarters ending in October, January, May, and August. I need to think about maximising the two “good” periods, and mitigating the damage¬†during¬†peak summer and winter.

Of course, climate change might make the summer period even worse. That is something scientists already say is being felt, and will only increase.

The cosmic ballet goes on...
The cosmic ballet goes on…

Positive Billing Into The Future

How will things look this summer? There will be more sunshine than in winter, but more electricity consumption as well.

The data I have for the year ending January 2016 (when the system was installed) suggests summer usage is a couple of percent higher than winter.

Will this be offset by any exports I do? How does the temperature affect this calculation in terms of air conditioner use? Pool pump running? More events in warmer weather?

These are questions I can’t yet answer.

For now, I have 258 days of finalised bills,¬†with a net electricity cost of $113.28 with referrals. That’s 43.9 cents per day for electricity, so I’m pretty stoked.

Even without the referrals, the figure is 71 cents per day, which is lower than my connection fee, and works out to $260 a year for electricity.

Even extrapolating the summer quarter as $1.30 per day (higher than winter), it works out to around $310 per year.

That still puts me in the box seat for a payback under 10 years, so its all systems go for now.

Relentless Self-Promotion Bit

Hey did you catch my recent video? I did a bit of off-road driving a couple of weekends ago. I’d love some more subscribers to my YouTube channel, so I can make more videos of things relating to solar panels and my own interests.