I seem to have hit a mental block on the best operating modes for solar + Powerwall on EV-TOU2 to minimize non bypassable charges (NBC's). Within the last 18 months, SDG&E has changed how they handle NBC's on NEM 2.0 (SDG&E Minimum Charge Adjustment Changed May 1st - Solar Panels - Solar Panels Forum). Previously, they were part of the $10 minimum monthly charge but now that $10 charge and NBC's are billed separately, so every kwh pulled from the grid effectively costs $.03 ish.
The Tesla app doesn't seem to have a good way to accommodate for this. Every kwh pulled from the grid will cost $.03 and can't be offset by solar generation, but the app only has buy/sell rates to use as calculation data points. I have already set the buy price at $.03 higher than sell to help minimize the NBC's.
Assuming one can charge from the grid, does it make sense to do so at night with super off peak rates? In this scenario. NBC's are incurred to charge up the PW and on a typical day, solar will power the house and export excess. At some point, PW would begin powering the house and all solar is exported and PW will continue to power the house until 12a when super off peak starts. Yes, we're powering the house with super off peak power at $.28/kwh when the buy price is $.40-$.80kwh, but that power has a real cash price of $.03 kwh. Base calculations would suggest house would use 9-11 kwh of PW power, but when PW knows it has stored power at $.28/kwh, it'll being using it at noon to power the house and export all solar, not just excess.
If grid charging is off, then PW is charged with power at shoulder rates $.40/kwh. This seemed ideal to minimize NBC's while at the expense of generating mid tier NEM credits. If one is an overproducer or has enough NEM credits banked, then this is less of a concern. However, I have noticed that in this case, while PW will power the house during peak (4p-9p) while all solar is being exported, it cease at 9p and pulls from grid at that time incurring NBC's and will continue to do so until 6a. The house would use 9kwh ish during this time excluding that car charging.
Self consumption mode could be idea to solve this to tell PW to avoid pulling from the grid as much as possible, but with a car charing at night, pulling power from PW is not ideal and they'll drain fast and may not be able to fully charge with solar the next day in the winter.
I realize this is trivial as far as real cash is concerned. Assuming grid charing a PW incurs the most NBC's and one charges 2 PW's from 0 to 100% daily, it's only $25 a month or about $300 a year, but it is a fun math problem to figure out. I've just hit a mental wall.
Perhaps self consumption mode and use 3rd party tools to switch PW modes during the car charging window is the best solution. While that was also fun to set up, it does have occasional issues and requires monitors to ensure it's still working, else you end up in the wrong mode at the wrong time.
What's your strategy to minimize NBC's with your Powerwalls?
The Tesla app doesn't seem to have a good way to accommodate for this. Every kwh pulled from the grid will cost $.03 and can't be offset by solar generation, but the app only has buy/sell rates to use as calculation data points. I have already set the buy price at $.03 higher than sell to help minimize the NBC's.
Assuming one can charge from the grid, does it make sense to do so at night with super off peak rates? In this scenario. NBC's are incurred to charge up the PW and on a typical day, solar will power the house and export excess. At some point, PW would begin powering the house and all solar is exported and PW will continue to power the house until 12a when super off peak starts. Yes, we're powering the house with super off peak power at $.28/kwh when the buy price is $.40-$.80kwh, but that power has a real cash price of $.03 kwh. Base calculations would suggest house would use 9-11 kwh of PW power, but when PW knows it has stored power at $.28/kwh, it'll being using it at noon to power the house and export all solar, not just excess.
If grid charging is off, then PW is charged with power at shoulder rates $.40/kwh. This seemed ideal to minimize NBC's while at the expense of generating mid tier NEM credits. If one is an overproducer or has enough NEM credits banked, then this is less of a concern. However, I have noticed that in this case, while PW will power the house during peak (4p-9p) while all solar is being exported, it cease at 9p and pulls from grid at that time incurring NBC's and will continue to do so until 6a. The house would use 9kwh ish during this time excluding that car charging.
Self consumption mode could be idea to solve this to tell PW to avoid pulling from the grid as much as possible, but with a car charing at night, pulling power from PW is not ideal and they'll drain fast and may not be able to fully charge with solar the next day in the winter.
I realize this is trivial as far as real cash is concerned. Assuming grid charing a PW incurs the most NBC's and one charges 2 PW's from 0 to 100% daily, it's only $25 a month or about $300 a year, but it is a fun math problem to figure out. I've just hit a mental wall.
Perhaps self consumption mode and use 3rd party tools to switch PW modes during the car charging window is the best solution. While that was also fun to set up, it does have occasional issues and requires monitors to ensure it's still working, else you end up in the wrong mode at the wrong time.
What's your strategy to minimize NBC's with your Powerwalls?
