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Discuss PV Panel - Output Deterioration in the Solar PV Forum area at ElectriciansForums.net


Regular EF Member
Hi all,

Looking at a project whereby client wishes to use some second hand (approx. 8 years old) panels, inverter etc. he has acquired from a demolished property.

Before getting subbies in to quote on re-installing them I am wondering your opinion on the output of the panels as someone has suggested (not on here) that an older panel may not be as efficient as a new one today of equivalent size? Could this be the case? If so would the cost of replacing them out weigh any benefit gained by re-using panels (especially if the addition output is minimal)!

They were also retro fitted to an existing roof and it has been suggested that they be re-installed flush with the roof tiles. Again views on this please, is it possible?



TJ Anderson

Forum Mentor
When I started to install that stuff 10 years ago IIRC correctly I remember for a panel to be MCS approved, part of the criteria was that it could lose upto 10% over 20 years. Dirt and bird crap is more of an issue lol as most roof mounted systems never get cleaned!!

Gary K

Regular EF Member
I assume that he is not considering claiming the FIT(if it still exists)?


Regular EF Member
bird crap is more of an issue
Tell me about it, the amount of s.....t Red Kites around here produce is amazing!!!

Living under the 'flight path'!!

Hi - based on this article I'd expect about 10% loss of output once they're cleaned up, compared with when they were new.

The Real Lifespan of Solar Panels - Energy Informative - https://energyinformative.org/lifespan-solar-panels/

There may also be some dead panels and notably the invertors do fail. I wouldn't reinstall without testing, just saying.
Thanks for the article, of course would all be tested and maybe best to recommend new panels in any case as they deteriorate in time.
System all purchased in good faith as 'working' but of course we've all been there!!

Gary K

Regular EF Member
I assume that he is not considering claiming the FIT(if it still exists)?
I assume so as there are plenty of companies around with panels on but not if he is purchasing second hand panels as I believe there has to be a paper trail from purchasing new


Regular EF Member
I've been out of the PV game for a while ....just passing through for a catch up.

As I recall it MCS required that panels guarantee no more than 10% degradation by 10 years and 20% by 20 years. I'm pretty sure that, in the real world, those targets are easy to hit.

I have an array of Panasonic (now Sanyo) panels which peaked at 3015W output when I first installed them in 2011, I noted a peak of 3000W a couple of weeks ago ...while that isn't a particularly scientific way of measuring any degradation, it does seem to suggest that they haven't degraded noticeably ....that, and, my annual generation levels don't seem to have dropped off to any extent that I've noted.

Panasonic/Sanyo panels are considered to be a 'premium' product and they use a hybrid technology ...it's possible that less costly, standard mono-crystaline or poyl-crystaline panels, may suffer degradation more.

The oldest PV system in Europe is located on the University of Applied Scineces, near Lugano, Switzerland, Their monitoring seems to conclude that long term degradation isn't as severe as the MCS product regulations might suggest.
Also see - First UK grid connected PV system 95% efficient 20 years later - https://www.solarpowerportal.co.uk/news/first_uk_grid_connected_pv_system_95_efficient_20_years_later_3256


Respected Member
If they were going to be ground or easilly accessable flat roof mounted then I'd say it's probably worth trying them.

If they're going to be pitched roof mounted, then almost certainly no.
If the plan is to fit them flush, definitely no.

There's a good possibility of some of them being damaged at removal or transport or refitting.
If they're easilly accessable,then the cost of sorting them out won't be too high.
If they're pitched roof mounted, then it's a scaffold job each time.

The problem with flush mounted would be getting matching sized panels if needed, something I've noted over recent years is becoming a problem as panel manufacturers go out of business or change the design / size.

I think you'll get a lot of negativity and unwillingness to re-install from installers when you go for quotes.

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