If your power utility offers net metering on an annual right-up basis, then less sun in the winter doesn’t matter. You would theoretically build up a credit on your power bill in the summer, and draw it down in the winter.

If your utility offers time-of-use metering, where the rates are higher during the sunny hours, then you may not need to size your system so large.

The value for sunlight hours – was that "peak equivalent sun," intended for sizing solar systems? In the winter here, the sun is out for 10 hours, but the equivalent sun is only about 2 hours, when dawn, dusk, and overcast weather are taken into account.

If your utility is set up such that they will never pay you cash for power, then it’s pointless to size your system so large that you might generate more than you use over the course of a year. This is in fact how the utility works where I live. The first year that our system was installed, we generated $80 more electricity than we used. We didn’t get a check for it, the balance was just set back to zero at the end of the year, as a donation to the grid.

What you should do is question a professional installer to look at your house and make a quote. They will probably know about the financing angle, too. Then choose whether it’s truly a value, or whether they’re trying to do a sales job on you.
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