I had a tough customer recently that grilled me on how we can put a 270W solar module on a 215W inverter. Fortunately, Enphase has a wonderful white paper on the subject. However, it got me thinking... Enphase has demonstrated that higher output panels in many climates (hot SW Florida included) can benefit from modules that far exceed the inverter rating, and even exceed the inverter's "recommended input" rating. Enphase has shown that 270W+ modules can show energy harvest on the M215 where it makes sense to "oversize" the module.
I also received a similar query from a rather uninformed plan reviewer in an area AHJ along similar lines. Fortunately I was within the "recommended input" rating on the spec sheet of 270W with a 265W module, but I wonder what would happen if I had paired the M215 with a 280W module on my plans, which are becoming readily available now in 60 cell modules with 300W modules on the near horizon. I'm pretty sure my plan would have been kicked back for exceeding the manufacturer's recommendation. My question, which applies to string inverters and microinverters, is how much is too much, what would happen if you paired an array that far exceeded the rating, and how do inverter manufacturers determine the recommended and/or maximum rating of the connected module or array? Also, why do some manufacturers have a simple recommendation while others have a "maximum" rating? Jason Szumlanski Fafco Solar
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