Are there any "rules of thumb" on crystalline silicone panel (not thin film) output (as a % of new) after say 5 or 10 years of age?

A wild guess, no more than 5% loss each year. In actuality, I think it's much less, maybe a couple/three % 1st year, and 1% each year after that. They are pretty rugged as long as the glass in intact and the innards stay dry.

figure about 1% per year as many have an 80% warranty after 20yrs. i'm not sure what the pv companies use to test that, but we can test for open circuit voltage and short circuit current and compare that to the published specs.

As Neil points out, PV panels have very long warranty's, 25 year with still 80% of name-plate rating is the industry standard

In the entire time I've been in PV/RE, I have never seen or measured any loss of output in Silicon panels or have read of any reports that have measured losses either. There is no technical reason for a panel to degrade, nothing in the cell degrades or is a moving part ... more than likely if a panel fails its an interconnection between the cell and can usually be repaired with a knife and soldering iron

Thanks so much for the information guys! Thats good to hear as I will likely be getting these used panels. I figure some will need a little TLC but I don't mind putting some work into them.

there may be other issues such as the silicone seals or whatever and i'd be curious as to what you are thinking of getting used?

This guy has about 1600W (original panel rating - probably less now) some ASE's (around 2000) some Siemens Pro 4JF ('96) and several new panels still in the box. Some are outside and some are in storage. All of them seem to be in good condition upon visual inspection and quick OC test with a meter.

May be somewhat difficult to connect these in usable strings but I was hoping to test them and see if there were enough sets that are similar output.

Don't know what these may be worth (as far as $/watt) given their age which is not too terrible if they are still within their 80% output figure.

Use this website as one of the "lowest" $/watt quotes...

http://sunelec.com/

If you can't get them for much less than new there--then they are probably not worth it (savings in shipping costs should probably be included in your personal comparisons).

-Bill

His asking is around 2.50/watt seems pretty firm on the price, probably around 500W of the 1600 are new in box or at least never been outside.

Go with the SunElec Sun branded Evergreen panels, new in box and only 75 cents/watt more

Used panels that are mix&match aren't really a bargain and 2.50 watt isn't that big of a deal, the SunElec panels 2 months ago were on sale for 2.75 watt new