DC to AC Derate Factor on Solar Panel Systems: What to Expect

What is the difference between DC ratings and AC ratings when it comes to solar?

That’s a question that we get a lot. They are essentially the same exact size system.

The DC reading is the name plate reading of the system. So, if we have solar panels that are 100 watts and we have 10 of them total, and consider the inverter to be 100% efficient, that means that it is a one kilowatt system or a thousand watt system DC.

The AC system rating is not that much different. Consider that we have 10 panels and the rating of each panel, based off temperature coefficients and additional factors, is 95 watts. If we assume the inverter is 97% efficient due to loss of heat or other coefficients, the same system would be considered a 920 watt system AC (or a 0.92 kilowatt system even though they are the same).

What are essentially the exact same systems are described differently. This is important because when you check out your contract or your system, much is DC (the nameplate) reading of the system. You may notice, however, that the actual output of the system is actually the AC rating.

That’s because your house runs off of AC power. So, its possible that the nameplate rate is 7600 watts but the system doesn’t get higher than 6800 and that is totally fine.


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