Not sure where else to post this so I thought I’d give this forum a shot....
I’ve got a 400amp main panel with average daily use of 75kW (excluding car charging) with a ~15.2kWp solar system. I’m getting constant outages in my area and am looking to purchase PW for whole home backup only.
I have the budget and space for 8PW’s but from what I understand SCE (my “awesome” utility) needs to “approve” how many PW’s I’m allowed to connect to my home.
Questions:
1) given my average daily use, what would be the ideal # of PW’s?
2) given the size of my solar system, how many PW’s is my utility likely to “allow”?
3) does tesla or the utility require/mandate an emergency load panel or may I simply use the PW’s to backup the entire Main Panel?
1) At a minimum, I imagine 4 would be required. Six power walls may not be needed if you are able to shed power usage during a power outage. Pool equipment, EV charging, and power for secondary structures could be moved to a non-backup electric panel. Use of an electric cloths dryer can be mitigated by hanging clothes under sun.
Consider average winter use (with an added margin) as your metric for 24 hour backup use. Summer use is higher (with AC loads) and can be mitigated with great summer production.
Note, the extra money spent on two more Powerwalls may be better spent connecting a
natural gas backup generator for maximum flexibility. The Powerwall can control the backup generator as needed.
2) Mokuzai has the best answer. As a reminder, the
Tesla Powerwall support page states, "To ensure reliable operation during power outages, at least one Powerwall is required for each 7.6 kW AC of solar included in the backup circuit." Three is the minimum for a 15.2 kW-DC system, though four makes better sense.
3) Without knowing how your home is wired, I assume Tesla will install your gateway and Powerwalls based on the below sample layout from the
Tesla Powewall Installation guide.
Non-critical loads would remain in the 400 A main panel. All your critical loads would be moved to a 200 A "backup-load" panel. A 200-400 A "generation" panel would include your Powerwalls, solar, and generator (if applicable).