August 2019, let there be sun!

For those that would prefer hearing the analysis!

It is now August and I’ve just had AGL send me my current energy bill. Well, based on my thoughts last month my credits are starting to increase. Take a look at the breakdown. Firstly with some stats from the Tesla app:

You’ll note that I am sitting on around 92% self-powered for the month. It seems I am doing a bit of troubleshooting for Tesla. I am working with them on their Cost Saving Time-based control mode. In this mode, my batteries aren’t meant to discharge in the off-peak time due to my tariff structure however this is a work in progress. Let’s dig into the actual data and note that the Tesla app calculates month days as first to last day of the month.

August figures without Solar and Powerwall 2

  • Daily Supply Charge – $1.054 per day * 31 = $32.67
  • Power Usage (from grid) – $0.23 per kWh * 659 = $151.57
  • Total bill = $184.24

August figures with Solar and Powerwall 2

  • Daily Supply Charge – $1.054 per day * 31 = $32.67
  • Power Usage (from grid) – $0.23 per kWh * 69.6 = $16
  • Solar Credits (to grid) – $0.20 per kWh * 417 – ($83.40)
  • Total bill = ($34.73)

Powerwall 2 Efficiency and Utilisation

  • Efficiency: 88.2% – up by 1.5% since the last report.
  • Utilization: 39% – up by 0.8% since the last report.

Powerwall specific costs

So there has been a lot of commentary on Whirlpool as to whether Powerwall is cost beneficial or not. A calculation by Whirlpool user swainstm has been provided to work through these costs. So lets use the following – From PW kWh * your usage tariff – To PW kWh * your FiT

Using the above calculation shows that for the month of August, my Powerwalls alone without any solar savings saved me $1.04.

Again, I am being transparent with this data. This data is calculated on a single rate AGL plan, which I am not actually on. It’s just easier to match data from Powerwall stats using a single rate as Tesla doesn’t break down the TOU rates which is what I am actually on.


Author: Adam

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