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.

 

 

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

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.

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

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.

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.

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.

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.

 

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.

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. 

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.

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.

1 hour ago, gamb00ler said:

would panels that infrequently face full sun actually generate more KWh over their useful lifespan than panels receiving more hours of full sun? 

 

 

The usual arguments I see online from PV haters is that Solar Panels are less efficient when they get hot so therefore they must produce less power when it's sunny 😎 

 

 

The drop in efficiency is very easy to calculate and is negligible compared to the increased solar energy production with increased solar radiance.

 

Biggest Solar Parks in the world are all in hot places

1st Golmud Desert Solar Park — China

2nd Bhadla Solar Park — India

3rd Mohammed bin Rashid Al Maktoum Solar Park — UAE

4th Pavagada Solar Park — India

5th Benban Solar Park — Egypt

6th The Tengger Desert Solar Park — China

7th Noor Abu Dhabi Solar Power Project — Abu Dhabi

 

As for panel degradation, my experience having had panels in Thailand for 8 years is that I did not see any noticeable loss in output.

My answer: YES

Reason: Electronic junctions probably degrade quicker if exposed to consistent high temperatures.

1 hour ago, carlyai said:

My answer: YES

Reason: Electronic junctions probably degrade quicker if exposed to consistent high temperatures.

That's true... but my question really is:  does the rate of panel degradation in full sun increase more than the photovoltaic output increases?  If the answer is yes, then the panel would produce more lifetime KWh if its exposure to full sun is reduced.

5 hours ago, BritManToo said:

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

Were they the cheapest panels you could find at that time?😉

Here in the states an engineer co worker of mine has a large solar system, starting off grid etc.  He says so many panels one buys on line are actually used panels.  So be careful of what you get and that you can verify its usage history as truly new or used

Some products, you simply get what you pay for.  Not rocket science.

7 hours ago, lom said:

Were they the cheapest panels you could find at that time?😉

 Mix of Trina, BlueTech and the usual budget panels.

I have 18Kw of inverters, so to allow for degradation I installed 23Kw of panels.

15 hours 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.

I think that your estimate of 50^oC of the temperature of solar panels on a sunny day is a tad on the low side. 

 

A couple of years ago during another topic covering a similar subject, I climbed up onto my carport roof where my solar panels are located, at mid day, on a good sunny January day, and took a temperature reading of the panels with a thermal gun.  Admittedly it's not the most scientific device, but gives a reasonable indication as to how hot the panels were.

 

 

Given that the panel's output is quoted from tests which have been conducted under laboratory conditions at 25^oC, they are then quoted to lose 0.X% for every 1^oC above that temperature (25^oC).  The 0.X% depending upon the make/model of the panel, but normally quoted in the range 0.3 to 0.5%. 

 

Hence, as shown above my panel temperature reading was 63^oC.  Therefore, my panels were 38^oC above the standard laboratory test figure (25^oC) which could mean a 19% reduction in panel efficiency (if taken at 0.5%/+1^oC).

 

It must be remembered that the temperature of the solar panels is just one potential cause of the loss of solar system efficiency.  There are a number of other factors which can also affect the systems efficiency.

14 hours ago, Bandersnatch said:

 

The drop in efficiency is very easy to calculate and is negligible compared to the increased solar energy production with increased solar radiance.

 

Biggest Solar Parks in the world are all in hot places

1st Golmud Desert Solar Park — China

2nd Bhadla Solar Park — India

3rd Mohammed bin Rashid Al Maktoum Solar Park — UAE

4th Pavagada Solar Park — India

5th Benban Solar Park — Egypt

6th The Tengger Desert Solar Park — China

7th Noor Abu Dhabi Solar Power Project — Abu Dhabi

 

As for panel degradation, my experience having had panels in Thailand for 8 years is that I did not see any noticeable loss in output.

Your absolutely correct, but just a couple of things to bear in mind:

 

The Solar Farms which you have quoted are massive, and I mean massive.  The owners of these Farms no doubt added sufficient extra panels during the design to cover any potential loss of efficiency resulting from the high temperatures.

 

What is not known, in reality, is how long the panels will last and give good quality output under those high temperature.  OK, the manufacturers quotes 25 years, but how long did they actually test the panels?

3 hours ago, 007 RED said:

OK, the manufacturers quotes 25 years, but how long did they actually test the panels?

 

Testing is done in a laboratory using accelerated conditions.

 

The level of degradation through exposure to high temperatures is significantly influenced by the quality of materials and manufacturing process.

Some examples :-

 

Discoloration reducing the amount of sunlight reaching cells.

Moisture penetration from constant high temperature and humidity.

Potential induced degradation causing power loss in photovoltaic cells.

Thermal stress created by large temperature swings can lead to cell delamination.

Protective back sheet material can degrade more quickly when exposed to high temperatures.

 

 

Solar panel performance and longevity will benefit from good  front and back air flow.

By coincidence, the NYTs just did an article about living in hot weather, where they showed solar panels with water cooling systems in Spain.

On 8/15/2025 at 5:06 PM, gamb00ler said:

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

 

Solar panels are cheap so a little bit of over sizing isn't going to cost you much.

 

When I first started looking at solar prices in Thailand about 10 years ago PV was over ฿20/Watt. The last panels I installed were less than ฿4/Watt and the prices are continuing to fall.

 

8 years ago I paid ฿10/Watt for 350W panels from a manufacturer that I'm sure nobody has ever heard of. They were still working fine when I sold them for ฿500 each and replaced them with 705W Tier One panels.

 

So I'm sure someone will ask "if they were working fine, why did you change them?"

 

I now have 2 EVs which draw a lot more power than what I used 8 years ago.