Friday, March 03, 2006

Quick solar tip: approved PV panels in California; STC vs PTC

Hey solarDwellers:

Make sure before you buy those panels, make sure it's on the California Energy Commission's official list of eligible equipment for rebates. (Tip is for those do-it-yourselfers out there, because a professional installer would already know this).

The list is also very useful in comparing the wattage ratings from one panel to the other when you're thinking of buying. Panels come with two wattage ratings: Standard Test Conditions(STC) and Performance Test Conditions(PTC). Think of the STC rating as under ideal, controlled environment testing conditions in the factory or the too-good-to-be-true rating! Think of PTC as more realistic, real world-type conditions, meaning the panels will produce less than the manufacturer's "ideal" STC rating.

For example, you could have a choice between a 175 watt(STC)panel from Shell or a 175 watt(STC)panel from BP Solar. But check it out! The California Energy Commission gives the rebate on the panels based on the PTC rating of the panels. In this case the BP Solar panel has a rating of 154 watts PTC, but the Shell has a rating of 158 watts PTC. In other words, the Shell panel will produce more watts than the BP in the real world, plus you'll get more rebate money back from that panel. If the prices on the two panels are close enough, it would be worth it to go for the Shell panel that produces more "real world" watts!

Just some silicon for thought . . .

--the solarDweller
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