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I just got PTO on my 7.2kW system, but the PTO letter from SDG&E says congratulations on your 6.553 kW system. I know there’s some inefficiencies, but is it normal for the utility company to factor that in?
Are you sure about that as Tesla inverters are either 3.8kw or 7.6kw?
My PG&E interconnect agreement from 2020 has my Solar CEC-AC rating listed as 7.556 kW and there is a footnote that says
CEC-AC (kW) = California Energy Commission Alternating Current, refers to the inverter efficiency rate (Quantity of PV Modules x PTC Rating of PV Modules x CEC Inverter Efficiency Rating)/1000
I have 24 PV modules made by Hanwha Q CELLS model Q.PEAK DUO BLK-G6+/SC 340 which have a nameplate value of 340W, but a PTC rating of 318.1W.
My inverter is a SolarEdge SE7600H-US with Efficiency rating of 99%.
Plugging those numbers into the formula I get 24 * 318.1W * 99%/1000 = 7.5581 kW which isn't quite right. So I round down on the panel rating to get 24 * 318 * 99%/100 = 7.5557kW which rounds to 7.556kW which matches what Tesla submitted on my interconnect form. Maybe Tesla uses integer PV PTC ratings or maybe the value changed from 2020 to today.
I find this formula strange as there isn't any consideration for an undersized inverter that would clip the AC output. Also, for myself I have panels in four different directions due to my roof surfaces and the most that I will every get out of my inverter is 6.2kW, so my rating is far higher than I could ever produce.
I just got PTO on my 7.2kW system, but the PTO letter from SDG&E says congratulations on your 6.553 kW system. I know there’s some inefficiencies, but is it normal for the utility company to factor that in?
Hi, this literally just happened today with me and w/ SDG&E (same sized system as you, too). Did you ever find out the reason why? I guess I should reach out to Tesla?