[00joe]

No tracking system. Here are some average numbers of hours of peak energy a day for a fixed system Portland Or 4.0, Chicago 4.4, Tampa 5.3, San Francisco 5.4

Total hardware costs are currently about $1.75 watt for panels, inverter and hardware. Fed Tax rebate is 30%.

[droithomme]

Thanks. Ok, your peak equivalent hours number for Portland OR using a fixed position is 4, implying an average of 365 * 4 * 4.5k = 6570kWh/year, correct?

The federal DOE site calculator for the same 4.5kWh fixed tilt plant gives 4580 kWh/yr for Portland (http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/US/...), ranging from 142 kWh/mo in December to 578kWh/mo in July. What accounts for the discrepancy between the two calculations?

[bzbarsky]

A good bit of the discrepancy is that the calculator assumes that the DC to AC conversion is only 77% efficient (see "DC to AC Derate Factor" in the calculator), while the naive calculation assumes 100% efficiency of conversion, right?

[jannotti]

Do these installations just pick the best single angle and stick to it all year? It seems like you must be able to get a reasonable benefit by adjusting your panels say, once a month.

[roel_v]

Yield from that isn't very big, and far outweighed by the cost of making the whole installation moveable. If you're going to put everything on a moveable frame anyway, it's better to have it servo-controlled so that it's at least adjusted continually.

[seigenblues]

fed tax rebate turns into a tax credit at the end of this year, btw! Move fast!