Skryll
Active Member
Look at how many kWh you use during the 4-9pm Peak period and also the 3-4pm and 9pm-12mid Part-Peak periods. From an arbitrage standpoint, there is no point to having more Powerwall battery (plus Reserve for blackout) than you use in one day during those times. So, unless you use more than 20kWh/day during Peak (unlikely in SF) you don't need the third Powerwall.
I have two Powerwalls but only 4.3kW of solar. My arbitrage is limited by my Summer Peak consumption (no A/C) of about 10kWh/day and then in the late Fall to early Spring, it is limited by my solar generation. With your larger solar system, you will probably only be limited by your Peak and Part-Peak consumption, not your generation.
To me, the incremental increase in Off-Peak price from EV-A (~$0.14/kWh) to EV2-A (~$0.17/kWh) is minor compared to the drop from Part-Peak (~$0.34/kWh) to Off-Peak (~$0.17/kWh) they imposed on our solar generation from 7am-3pm. It used to be that the vast majority of my solar generation earned Part-Peak prices and I could use double the kWh during Off-Peak for EV charging. No more. It's 1:1 solar to EV charging because they're both Off-Peak.
Interesting. We are on the 'far east bay' so 90F summers are normal and the AC use is horrendous. Also our dryer doesnt have a timer on it and so doesnt run over night, probably pulling a good 4kW/h so between cooking and all that, the summers may easily be over 20kWh.
Mhm, a new dryer may be cheaper than the third powerwall... or replacing the AC with one that isnt from the 80s, or replace windows, but those two projects cost a lot more than the extra powerwall.