I am currently in the process of getting solar from a local company (did not work out with Tesla due to type of roof, and I wanted microinverters anyway). I had placed the order for 2 Powerwalls as well, but that will now be considered next year or later. I am in SCE territory, and wanted to review my load calcs, backfeed calcs and panel options here.
Current Panel = 200A main breaker, no idea about bus as there is no label anywhere.
Objectives:
a) 60A for solar (34 x 360W LG panels, so 12.24kW) now
b) 14-50 outlet or hard-wired charger for EV (planned for near future)
b) 2 Powerwalls at sometime in future
What I have understood from the local company is that total backfeed cannot be more than 120% of the bus amp rating. So assuming 200A bus, max backfeed = 240A.
And 60A for solar + 30A*2 for 2 powerwalls = 120A backfeed. --> Is this correct?
Load Calcs and Backfeed Calculations
=====================================
Tesla did load calc with Optional way using breaker values, and came up with 123A (without EV outlet). Proposed (I think) derate to 125A, 60A for solar, 60A for 2 powerwalls = 245A backfeed. This is >120% of 200A panel, so not sure if that was going to be feasible.
My load calcs - Did load calcs both ways using appliance nameplate ratings, Standard and Optional. After including 48A for the 60A breaker for hardwired Tesla EV charger, I came up with these numbers:
1) Standard = 171A
2) Optional = 147A
So I see the following options for my electric panel:
1) Keep current 200A panel (max 240A backfeed):
a) Derate to 150A, 60A for solar, 30A for only 1 powerwall = 240A backfeed
2) Upgrade main panel to 200A/225A (max 270A backfeed):
a) Derate to 150A, 60A for solar, 60A for 2 pwerwalls = 270A backfeed
b) Derate to 175A, 60A for solar, 30A for 1 powerwall = 265A backfeed
c) No derate at this time so use full 200A, 60A for solar = 260A. When get solar choose either of 150A or 175A derate options at that time.
3) Upgrade main panel to 400A. Waiting for meter spot from SCE to find if it is even feasible.
4) Go the GMA route, upgrade panel later when get powerwalls.
Does the above reasoning and calculations sound correct (assuming load calc is ok)? I find it hard to believe that all homes with similar-sized solar and 3 or more Powerwalls have 400A service? What am I doing wrong here?
If it matters, I have 40A breaker for a sub-panel for spa. I don't need to backup this or the EV outlets if/when I get the Powerwalls.
Which option would you recommend for the electric panel?
Current Panel = 200A main breaker, no idea about bus as there is no label anywhere.
Objectives:
a) 60A for solar (34 x 360W LG panels, so 12.24kW) now
b) 14-50 outlet or hard-wired charger for EV (planned for near future)
b) 2 Powerwalls at sometime in future
What I have understood from the local company is that total backfeed cannot be more than 120% of the bus amp rating. So assuming 200A bus, max backfeed = 240A.
And 60A for solar + 30A*2 for 2 powerwalls = 120A backfeed. --> Is this correct?
Load Calcs and Backfeed Calculations
=====================================
Tesla did load calc with Optional way using breaker values, and came up with 123A (without EV outlet). Proposed (I think) derate to 125A, 60A for solar, 60A for 2 powerwalls = 245A backfeed. This is >120% of 200A panel, so not sure if that was going to be feasible.
My load calcs - Did load calcs both ways using appliance nameplate ratings, Standard and Optional. After including 48A for the 60A breaker for hardwired Tesla EV charger, I came up with these numbers:
1) Standard = 171A
2) Optional = 147A
So I see the following options for my electric panel:
1) Keep current 200A panel (max 240A backfeed):
a) Derate to 150A, 60A for solar, 30A for only 1 powerwall = 240A backfeed
2) Upgrade main panel to 200A/225A (max 270A backfeed):
a) Derate to 150A, 60A for solar, 60A for 2 pwerwalls = 270A backfeed
b) Derate to 175A, 60A for solar, 30A for 1 powerwall = 265A backfeed
c) No derate at this time so use full 200A, 60A for solar = 260A. When get solar choose either of 150A or 175A derate options at that time.
3) Upgrade main panel to 400A. Waiting for meter spot from SCE to find if it is even feasible.
4) Go the GMA route, upgrade panel later when get powerwalls.
Does the above reasoning and calculations sound correct (assuming load calc is ok)? I find it hard to believe that all homes with similar-sized solar and 3 or more Powerwalls have 400A service? What am I doing wrong here?
If it matters, I have 40A breaker for a sub-panel for spa. I don't need to backup this or the EV outlets if/when I get the Powerwalls.
Which option would you recommend for the electric panel?