question about solar panel life span and total output

[gamb00ler]

From what I've read panels deteriorate faster with higher temperatures.

 

I am hoping that several weeks of overcast skies is extending the life span of my panels. 🤞 I can't measure my panel temperature but I would assume that it would be much lower than in full sun.

 

My question is:

would panels that infrequently face full sun actually generate more KWh over their useful lifespan than panels receiving more hours of full sun?  Assume panels lifespan to end when their output drops 20% from when new.

 

 

[Crossy]

A very interesting question methinks!

 

Now I think I know the answer but let's see what other members think before I reveal my thinking

[Schoggibueb]

Maybe this can help a bit. The higher the temperature on the panels, the lower the output gets. On a sunny day you will have (never measured) I guess around 50°C on the panels. That would be around 15% less output if I remember correctly.

[Schoggibueb]

Means on a standard module you will have after 25 years still 83% performance. Don't worry too much about this.

[BritManToo]

32 minutes ago, Crossy said:

A very interesting question methinks!

 

Now I think I know the answer but let's see what other members think before I reveal my thinking

String 1

4x 340w panels purchased in 2022 now produce 500w at midday on a sunny day for me.

so 30% of spec. (3,500bht each)

 

String 2

4x 580w panels purchased in 2025 produce 1,800w at midday on a sunny day.

so 80% of spec. (3,000bht each)

 

Hoping the new ones wear better than the older ones.

[Muhendis]

Sunlight is essential for a solar panel to produce electricity but there is an element of sunlight which is quite destructive to pretty well all substances.

 

UV radiation.

 

This UV light will slowly degrade a solar panel reducing it's efficiency unless it is filtered out. Trouble with that is it also reduces efficiency of "normal" light photons.

 

The question about cloudy days extending the life of panels well that is perhaps true but that really defeats the object of what a solar panel is all about.

 

Modern panels should last something like 25 - 30 years in daily use with plenty of bright sunshine. What is meant by that is the efficiency will deteriorate such that the panels output has reduced to 80% of it's designed maximum. It still works just fine but the loads it will drive will have to be smaller.

[Crossy]

2 minutes ago, BritManToo said:

4x 340w panels purchased in 2022 now produce 500w at midday on a sunny day for me.

so 1/3 of spec.

 

4x 580w panels purchased in 2025 produce 1,800w at midday on a sunny day.

so 2/3 of spec.

 

Hoping the new ones wear better than the older ones.

 

Did you actually record values when those panels were new??

 

There are a massive number of variables at play here, hard sums.

[BritManToo]

16 minutes ago, Crossy said:

Did you actually record values when those panels were new??

There are a massive number of variables at play here, hard sums.

Yep, was originally getting 2,500w out of 10 of them (60% spec).

But dropped to 1,500w after 2.5 years. (9am to 2 pm)

Then I started replacing them.

New ones, getting 2,400w out of 5 of them (80% spec). (8am to 5pm)

 

Panels in the same rack, shaded after 2pm, took out 6 of the failing panels and replaced them with 4 new ones (now 5).

 

The new panels also start producing an hour earlier, and stop producing 3 hours later.

N-type, mono, double sided, split panels are the bees knees IMHO.

 

[gamb00ler]

I don't know how useful an answer to my query would be.  My motivation for asking was mostly intellectual curiosity.  I can't think of how to reap a financial or practical reward after knowing the answer.

[RMK54]

19 minutes ago, Schoggibueb said:

Maybe this can help a bit. The higher the temperature on the panels, the lower the output gets. On a sunny day you will have (never measured) I guess around 50°C on the panels. That would be around 15% less output if I remember correctly.

As an engineer, data reigns supreme in a discussion like this. I’ll add that this is theoretical, based in a test environment! So, in actual use, depending on the installed environment, life expectancy could change drastically. Personally, I have my pros and cons regarding them and believe one’s personal need outweighs technical considerations. 

[Crossy]

9 minutes ago, BritManToo said:

Yep, was originally getting 2,500w out of 10 of them (60% spec).

But dropped to 1,500w after 2.5 years. (9am to 2 pm)

Then I started replacing them.

New ones, getting 2,400w out of 5 of them (80% spec). (8am to 5pm)

 

Panels in the same rack, shaded after 2pm, took out 6 of the failing panels and replaced them with 4 new ones (now 5).

 

The new panels also start producing an hour earlier, and stop producing 3 hours later.

N-type, mono, double sided, split panels are the bees knees IMHO.

 

 

It will be interesting to see if the older panel's wear-rate evens out after an intitial drop.

[BritManToo]

13 minutes ago, Crossy said:

It will be interesting to see if the older panel's wear-rate evens out after an intitial drop.

Old panels purchased in 2022, big 50% drop in production earlier this year 2025, 1 panel failed completely.