Starting this thread to discuss Powerwall operation strategies for PG&E customers that are net generators. Trying to keep track of all the nuances can make your head spin. I'm on NEM2 EV2A and have made the following observations/conclusions:
The most efficient use is directly consuming from solar production.
The second most efficient use is drawing from the Powerwalls but you lose about 10% in round trip efficiency losses.
The least cost effective method (for net generators) is drawing "banked" power back from the grid. You get compensated at the wholesale rate at your annual true-up for any excess generation so any power you draw from the grid reduces that amount. Additionally you pay non-bypassable charges (NBCs) on any power you draw back from the grid.
Then there are pesky Time of Use (TOU) rates. My understanding is that you could be a net generator in power but still wind up with consumption charges if you drew more power during peak rates than you built up credit for. I.e., if your total charges are more than your total production value (in dollars) then you need to pay the difference. But you don't get compensated extra if your production value exceeds your consumption charges. And you can't use excess compensation to offset NBCs.
Additionally there are the minimum monthly charges. These appear to be useable for NBCs (as is the compensation for excess power generation) but I don't know what happens if the minimum monthly charges exceed the NBCs. And additionally there are the climate credits that come into play.
And lastly, one thing to take into consideration is wear and tear on the Powerwalls. For someone that only uses about 50% of their capacity on average this probably isn't much of a concern, they will probably just die of old age. But for someone that is using close to 100% of their capacity daily they might want to take ways to reduce Powerwall usage into consideration.
I'm an net generator (barely). I have a 10kW solar system and 3 Powerwalls (and no EV). I have a heat pump (but have other sources of heat). My winter electricity consumption exceeds my summer consumption. During the winter I set my reserve at 50% (I live in an area of frequent power outages). I was using Time Based Control (TBC) but the NBCs were hammering me. I considered switching to Self-Powered but was concerned that without a way of telling the Tesla app to avoid drawing power during peak rates I would get hit with excess peak consumption charges. Tesla really needs a hybrid option in their settings; self-consumption but a way to tell it to plan to avoid drawing power from the grid during peak rates.
The Netzero app (great app if you haven't tried it) now has the ability for basic automation. In Self-Consumption mode if I make it to 80% State of Charge by 3 pm I can usually make it through peak without hitting my 50% reserve. I have set up automations to increase my reserve and turn on grid charging in 3 increments (60%, 70%, and 80%) every 45 minutes starting at 12:45 pm. That way I have a backstop to make it through peak and so far it has been working good. Usually this only kicks in if it is cloudy or raining. There is a little bit lost due to the 10% round trip efficiency loss but the insurance is worth it to me.
I'll see how good this works through this summer and next winter.
The most efficient use is directly consuming from solar production.
The second most efficient use is drawing from the Powerwalls but you lose about 10% in round trip efficiency losses.
The least cost effective method (for net generators) is drawing "banked" power back from the grid. You get compensated at the wholesale rate at your annual true-up for any excess generation so any power you draw from the grid reduces that amount. Additionally you pay non-bypassable charges (NBCs) on any power you draw back from the grid.
Then there are pesky Time of Use (TOU) rates. My understanding is that you could be a net generator in power but still wind up with consumption charges if you drew more power during peak rates than you built up credit for. I.e., if your total charges are more than your total production value (in dollars) then you need to pay the difference. But you don't get compensated extra if your production value exceeds your consumption charges. And you can't use excess compensation to offset NBCs.
Additionally there are the minimum monthly charges. These appear to be useable for NBCs (as is the compensation for excess power generation) but I don't know what happens if the minimum monthly charges exceed the NBCs. And additionally there are the climate credits that come into play.
And lastly, one thing to take into consideration is wear and tear on the Powerwalls. For someone that only uses about 50% of their capacity on average this probably isn't much of a concern, they will probably just die of old age. But for someone that is using close to 100% of their capacity daily they might want to take ways to reduce Powerwall usage into consideration.
I'm an net generator (barely). I have a 10kW solar system and 3 Powerwalls (and no EV). I have a heat pump (but have other sources of heat). My winter electricity consumption exceeds my summer consumption. During the winter I set my reserve at 50% (I live in an area of frequent power outages). I was using Time Based Control (TBC) but the NBCs were hammering me. I considered switching to Self-Powered but was concerned that without a way of telling the Tesla app to avoid drawing power during peak rates I would get hit with excess peak consumption charges. Tesla really needs a hybrid option in their settings; self-consumption but a way to tell it to plan to avoid drawing power from the grid during peak rates.
The Netzero app (great app if you haven't tried it) now has the ability for basic automation. In Self-Consumption mode if I make it to 80% State of Charge by 3 pm I can usually make it through peak without hitting my 50% reserve. I have set up automations to increase my reserve and turn on grid charging in 3 increments (60%, 70%, and 80%) every 45 minutes starting at 12:45 pm. That way I have a backstop to make it through peak and so far it has been working good. Usually this only kicks in if it is cloudy or raining. There is a little bit lost due to the 10% round trip efficiency loss but the insurance is worth it to me.
I'll see how good this works through this summer and next winter.
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