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

The other thing to consider--are you getting more panels that you need (could be a waste of money) or fewer panels than you need (still need to buy some more used/new to fill out the array--and if these are "non-standard" in voltage or current--it could be difficult to mix and match).

Plus you have to see if the warranties are still valid (original receipts, company in business, will honor 2nd owner, etc.).

Against how much it will cost you to get new-in-box shipped to your front door (not cheap either).

-Bill

skygazer,
on top of all that has been said, you still don't know if they are good or not. i would think the guy should lower the price down to $2/w or less for such used pvs even if you find them in good working condition simply because you can buy new at a very cheap price. if they are that valuable to that guy then maybe he should be keeping them and in fact why is he getting rid of them? hmmm

Thanks for all of the good points guys, I was very interested in purchasing the panels but much less so now. I feel like all of them likely work but there is definitely no warranty.

I looked on the sunelec website and the lowest I saw panels listed for were $3.60/watt at quantities of 25 or more, is there another listing I couldn't find?

Also how often do the panels go on sale at the $2.75/watt level, it seems like that wouldn't happen with all of the interest in renewable energy (supply/demand). I only regret that I didn't get into solar sooner, I have always had the desire but never acted on it.

It does not seem to be predictable when the panels go on sale--the cheapest I saw was some 6-9 months ago (???) at $2.50 per watt (IIRC)... And that was like over a weekend (put up on Friday and taken down on Monday--from what I saw).

Most of the time, if you get $0.10 on the dollar--that is the usual discount for used, working equipment.

$0.50 on the dollar is getting pretty close to the wholesale cost of stuff... Not a great discount--but if the product is good, then 50% off is better than retail.

-Bill