PV Output - Ageing system

oldskoo1

Hi all 
Does age affect maximum output? 

Any quantifiable maintenance that can improve output, ie cleaning? 

My panels are about 7 years old. 4kW system, appears to be running ok. I’ve never cleaned my panels as it’s a 3 storey house. 

I admit I rarely check daily output so I’ve lost touch with what the peak should be in certain scenarios. 

It’s 4:40pm, early May and the house is 184 degrees south with a close to ideal pitch. Output right now is 2,800watts in direct sun, it’s fairly hot so panel temperature might be around 37c looking at my direct sun thermometer and 18.5c on the inverter. 

I thought it was a tad low, expected >3kW but maybe it’s because it’s 4pm. 

Thanks 

EcoScruples

Check it against Solcast, use the efficiency reduction for 7 years and you should see roughly what you will get.
2.8kw at 4pm doesn't sound bad at all.

oldskoo1

EcoScruples said:

Check it against Solcast, use the efficiency reduction for 7 years and you should see roughly what you will get.
2.8kw at 4pm doesn't sound bad at all.

Thanks, what a great tool. Looks like I’m exceeding the forecast even without adjusting the efficiency factor. 

gefnew

I have had panels since 2011 and can say looking at records do not see any major reduction in output.
Original quote stated 3470Kwh a year, averaged 3700Kwh per year with no cleaning or maintenance required on any part of the installation (touch wood now).

oldskoo1

That’s very encouraging, thank you

Martyn1981

Yep, 11yrs in and can't see any obvious drop yet. Not even a gut feeling that there's a downward trend, perhaps UK sunshine levels just aren't enough to wear the PV ..... much?

QrizB

Martyn1981 said:

Yep, 11yrs in and can't see any obvious drop yet. Not even a gut feeling that there's a downward trend, perhaps UK sunshine levels just aren't enough to wear the PV ..... much?

My system was 10 in January and, like Martyn, I can't see a trend.

There's some variation year-to-year but an overall tendency? I can't tell.

Yes 2021 was my worst year ever, but 2020 was my best!

EcoScruples

That's pretty consistent, really encouraging that after a decade, panels still perform at pretty much peak levels.
Like all things, as long as they're well installed I don't think people will have too much to worry about.
What about inverters? They should last longer than 10 years but how do you know when they need changing? Do they just give up?

Spies

You could actually browse www.pvoutput.org and check out the older systems to see if they've recorded any considerable degradation. 

QrizB

EcoScruples said:

What about inverters? They should last longer than 10 years but how do you know when they need changing? Do they just give up?

I think they just give up, although there's probably some uncommon failure mode that would see them run at half power or whatever.

I'm still on my original one.

ispookie666

I would say yes due to two factors 

1. personal experience.  I did add a few posts to this thread 
2. There is a large solar farm (started generating 2015) close to my home and they have changed all their panels this year. The panels used to be the old blue colour and are black.  I'm sure as a business they probably did all sort of calculations to reach at this conclusion.