Declines in solar panel output

[Anonymous]

We had panels installed 5 years ago. Looking back over archival data, it looks llle the panels are on average decreasing in output 5-10% per year. Is this normal? I’m regretting getting them because it seems like this is not really worth while. This March, the 18 panels produced 400 kWh.

[Anonymous]

They should lose 1% or less per year. Of course conditions may be more or less favorable for generation at any given time but our experience is that over a year that more or less balances out.

I have never heard of anyone losing 25-50% output in 5 years but if that really happened you should talk to the installer.

[Anonymous]

How often are you cleaning them?

[Anonymous]

Anonymous wrote:How often are you cleaning them?

We’ve never cleaned them. I posted on the home forum asking for a recommendation for a cleaner and everyone said that you don’t need to clean them around here.

[Anonymous]

You need to clean them. We live in SoCal and clean ours every year.

[Anonymous]

Anonymous wrote:

Anonymous wrote:How often are you cleaning them?

We’ve never cleaned them. I posted on the home forum asking for a recommendation for a cleaner and everyone said that you don’t need to clean them around here.

Clean them and see if your output improves.

[Anonymous]

Anonymous wrote:You need to clean them. We live in SoCal and clean ours every year.

That's because it doesn't rain where you are. It rains and snows here, so we don't need to clean them.

OP should probably clean them just to show the installer that's not the issue, but this really sounds like bad equipment. OP, what was promised in the sales paperwork?

[Anonymous]

OP, do you have one or two inverters? One of your inverters may have failed and needs to be replaced. You need to have your system checked.

[Anonymous]

Yes, this sounds like exactly the kind of disappointment a lot of homeowners are waking up to.

5 to 10% output loss per year is not normal for properly functioning solar panels. Most reputable systems degrade closer to about 0.3% to 0.8% annually, not massive yearly drops. If someone is seeing that kind of decline after only five years, something is wrong, whether it's inverter issues, failed panels, poor installation, wiring problems, shading changes, or misleading original projections.

And that is where many people feel scammed. The sales pitch is usually "huge savings, guaranteed returns, low maintenance," but when production underperforms, suddenly the homeowner is stuck chasing warranty claims, arguing over monitoring data, and finding out there is no real guarantee of savings at all.

We know someone dealing with the same thing. Big promises upfront, then later it becomes "well results vary" and if the system is not functioning properly or underperforming, you may get little or nothing back while still having paid the full install cost.

This industry has been way too full of aggressive sales tactics, unrealistic payback timelines, and companies disappearing or dodging accountability after the install. Some systems work well, but far too many homeowners were sold dreams instead of real numbers.