Thanks. It looks like a 4500W fixed tilt system in Seattle would generate 150 to 572 kWh, depending on the month. 4364 kWh per year, which is not too bad. 1 axis tracking brings it to 5492kWh, 2 axis tracking to 5819kWh.
It might become reasonable in Seattle at some point, depending on the costs of installing a system with tracking. One should also factor in that peak output decreases over the life of the panels in figuring out lifetime cost/benefit, and not just look at output numbers from the first year.
It's important to establish what specific area we are talking about in these discussions and what particular sorts of systems we mean and their actual complete costs. Not everyone lives in Florida or Hawaii and my understanding is that tracking systems are quite rare and have their own issues. I've only seen one tracking system myself, it was at a school installation that was done in a field. I have not yet seen them on rooftop installs. There is little information about them but often estimates include numbers assuming tracking.
Tracking is only helpful in sunny areas, certainly not in a cloudy place like Seattle.
Given the rate solar PV panel prices are falling, however, PV in Seattle-type climates (and in Germany like the OP discusses) may be economic much sooner than many people expect.
"Tracking is only helpful in sunny areas, certainly not in a cloudy place like Seattle."
This is not strictly correct, tracking does help as the numbers from the DOE calculator show. However, the cost of purchasing, installing, and maintaining a tracking system will cancel out some, or possibly all of the gain. How much so is not clear.
In this case, a 4500Wp fixed angle installation, which appears to be available for around $12,000 not including installation or installation brackets generates 4364kWh per year in Seattle, saving the homeowner $279.30 in annual electric costs given the alleged 6.4ยข/kwH rate in Seattle (which seems very low to me). This is equivalent to a 2.3% return on the investment, with, unlike in savings, the principal is non-recoverable and expires after 25 years as the panels reach their end of life.
The numbers are better for other cities true. The DOE calculator gives 5491 kWh/yr for a 4500Wp fixed angle installation in Hawaii, with 18.1 cent electricity. Over a year, the electricity value is $993.87, an 8.2% annual return, but again, with the principle not returned and the investment expiring after 25 years.
http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/US/...
It might become reasonable in Seattle at some point, depending on the costs of installing a system with tracking. One should also factor in that peak output decreases over the life of the panels in figuring out lifetime cost/benefit, and not just look at output numbers from the first year.
It's important to establish what specific area we are talking about in these discussions and what particular sorts of systems we mean and their actual complete costs. Not everyone lives in Florida or Hawaii and my understanding is that tracking systems are quite rare and have their own issues. I've only seen one tracking system myself, it was at a school installation that was done in a field. I have not yet seen them on rooftop installs. There is little information about them but often estimates include numbers assuming tracking.