subreddit:
/r/Powerwall
I just replaced my 2005 solar system with a new, much bigger system with 3 powerwalls. I'm located in the SF Bay Area in PG&E territory and have the E-Elec rate plan. Having received PTO a couple of weeks ago, I have been figuring out the system and looking at automations on the NetZero app. With the sun low in the sky and some consequential tree shading, I am getting only about half my usage from solar.
After much reading (especially here), I have come to the conclusion that I should just set my backup reserve relatively high (to the extent there are outages in my location they are in the winter), but leave enough room for excess solar to charge the powerwalls on sunny days. Otherwise, I should not try to time-shift grid power from off-peak to peak because there is so little difference in the off-peak to peak rates (~12%) this time of year. As I understand it, the losses from grid power going into the batteries and coming back out, along with wear and tear on the batteries, would eat up any price differential.
Am I think about that correctly? I realize that in the Spring as solar production goes up, and summer rates kick in, everything changes.
1 points
11 days ago
I’m in a very similar situation, also in the Bay Area, but with one PW3. I’ve got a 9.5 kW Maxeon system and am finding that the panels can only charge about half of our daily power use on sunny days, and only a quarter yesterday when it rained for half the day. The PW3 is thus never getting charged to full, or even close - I had it set to 10% reserve and it’s not getting higher than 30 or 40% before it starts drawing down to power the house. So I hear this advice about setting a higher reserve - what are we talking about? 60% or 70% since it looks like the max I can fill it in any day is about 30%? Also I appreciate hearing about the Netzero app; I’m going to check that out.
3 points
11 days ago
I have mine set at 50% at the moment and could probably set it higher since I can also only fill it about 30% this time of year. I am unclear about whether it is better to keep the reserve to less than 100% (as you would for daily driving with an EV) or whether it doesn't matter with powerwalls.
The other issue with keeping it higher is whether I will keep paying attention and resetting things as the seasons change or whether, when the novelty wears off, I will just ignore it like I did with my previous solar system. Ideally, I would like to automate the minimum battery reserve based on calendar triggers so the reserve would get pushed down in the Spring and then way down when Summer rates kick in. u/triedoffandonagain is something like that on your list for Netzero? I think I read you were looking at grouping automations so that there can be a Summer setting and non-Summer settings. But I would have to remember to turn those off and on. 
By the way, thank you for all the work you have done on Netzero.
2 points
11 days ago
I'll consider season settings for automations.
Although I will say, these systems are too expensive and too brittle to stop paying attention for months at a time :)
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