last month I was 99% off the grid. I charge my car when PW's are charged, like at 1pm, so most of the time I do not charge them from the grid unless I have no choice. So I believe I am doing everything I can to no pull from the grid? Is there something I am over looking?
In the winter I am stuck since I produce so much less solar than I use from my heat pumps. I believe you have gas heat?
If so this is the thing pulling from the grid we are stuck with, even with lots of batteries. I cannot get them filled in winter
Yeah, you are doing great!
Is there something I am over looking?
Since I'm trying to understand optimizing under NEM2, this is a fun query for me.
Thanks again for sharing your true-up B&W with me. That shows a lot, but PG&E does not know how much solar you produced nor how much your home and car consumption was.
We do know your true-up adjustment was only $82.03 and was equal to your NBC's minus the $130 you'd already paid in on your monthly bills. But this means that no mater what you do, you can not reduce the total cost more than $82. So the question boils down to this: if you wanted to reduce your cost that much, how would you do it.
The cost is driven by your Non-Bypassable Charges which amount to around 3 cents on every kWh you import. So you'd need to reduce your imports by around 2,700 kWh. One way is to do that much more car charging during sunny times. Once your PWs are full, without the car, your excess solar, i.e. solar minus house consumption, is exported. If you instead charge your car at the same rate as you would export, you don't export, and you don't need to import that amount later when the sun isn't shining. At 11 kW charging rate, this would be roughly 245 hours of car charging, nearly an hour per day on average, of course more in summer and less in winter.
This requires adjusting the car charge rate, or in your case also how many cars you are charging. Your solar, at up to 30kW is nearly enough to charge 3 cars at once at 11 kW each. I don't have it yet, but current Tesla car software and app allow Charge on Sunshine which is supposed to do the math and adjust the charge rate for you. Of course this only works if the cars can be plugged in during daylight after PWs are full. Car charging before PWs are full can absorb the power which means the PWs will not charge as soon, and so if your car in there in the morning but not the afternoon, it is still possible to use the sunlight directly, but this I think is not supported by CoS.
Another approach is to have the house use the grid as little as possible, regardless of TOU periods. In winter, if PW can cover your needs all night till sunup, you are golden. But with electric heat, short days and storms, there is not a lot you can do. Where a coat indoors? Still, any reduction of consumption does reduce NBCs, and any shift of consumption to solar production times also helps. Perhaps adjusting the house temp up and down a bit would let you use it as a thermal energy storage to time shift the heat pump draw into solar times? How many kWh does it take to raise the temp of the entire house by 1 degree? It may not be negligible.
But to widen the query a bit, what if you did something that increased NBCs, but increased your net generation credits even more?
As for PW controls, Export Everything increases both your exports and your imports. As a net generator, any incremental exports earn you NSC of around 8 cents, but cost you NBCs of around 3 cents, still a small net profit. Frankly, I don't even know if the net surplus compensation is TOU or seasonal, and how this would affect PW optimization. But the profit margin is small in any case.
Grid Charging on low solar days does let you time shift more consumption to off peak, thus decreasing your cost. If you didn't grid charge you'd import nearly the same kWh later on, so GC in this case does not increase NBCs. Combining GC and EE will probably give you that small EE profit on a bit more kWh, but it will be hard to see because it increases both your credit and your costs.
One aspect I'm less up to speed on is the Self Powered mode. I've been doing some simulations of my system, and it appears that this mode results in the lowest NBCs. I don't understand why this is, if it is true, and I certainly don't know if your case would be the same. In my case, it make me owe more NEM charges, so the NBCs wouldn't matter, which I why I haven't tried to figure it out.
But again, no matter what you do, the best you can get by reducing your NBC's is $82, which is probably not worth the effort of trying. Increasing your net generation compensation, likewise may be too small to be worth it.
