Nothing lasts forever. But why does the output of solar panels decrease with time?
Over time, solar panels degrade due to factors such as UV rays exposure, extreme temperature changes, soiling, unwanted chemical reactions in the semiconductor material, and adverse weather events such as hail, strong winds, ice, dust, salt, etc.
Degradation is a normal characteristic of all solar panels and something that’s bound to happen.
Therefore, to make a sound decision on the solar panels to acquire, you must first understand their lifecycle and degradation process.
With this definitive guide, you’ll learn how solar panels degrade and what you should expect from them throughout their lifetime.
How long do solar panels really last?
It's considered that the useful life of solar panels ends when the production goes below 80% production.
This usually takes around 20-30 years. According to manufacturers, the energy production of solar panels in their useful life is optimal to meet the energy needs of average users.
Thanks to manufacturing technological advances, the longevity of solar panels has really improved over the years, and it can only get better.
The main factor determining solar panels' lifespan is their degradation rate, and that’s why we’ve dedicated this guide to discuss this topic.
What happens when solar panels hit their lifespan?
When solar panels hit their lifespan, they continue to produce energy but at a much lower efficiency level, so don’t fall for the thought that they’ll storm working completely.
When solar panels clock their expected lifespan, you can either:
Decommission (remove, without necessarily replacing, the entire solar panel system and sell it to recyclers or DIY consumers), or
Repower (remove and replace the old module with new technology).
Since the lifespan of solar panels is typically how fast they degrade, it’s crucial to understand what solar panel degradation is.
What is solar panel degradation?
Definitively, solar panel degradation is the decrease of solar panel output over time. Here are the common forms of solar panel degradation, their causes, and the problem they bring to the solar system:
| Form of degradation | Cause(s) | Related problem |
| Discoloration | Exposure to heat and UV rays | Reduces the sunlight that reaches the solar panels |
| Delamination | Manufacturing issues with the laminate | It’s a gateway to moisture that causes corrosion of the solar panels |
| Flexing or dynamic mechanical load | Mechanical stresses such as strong winds | Fatigue/failure of the interconnections |
| Microcracks in the silicon of the solar cells | Mechanical and thermal stresses | Increased internal resistance and thus a rise in cell temperature when current passes (Hot spots) |
| Shadowing | Chemical reactions in the semi-conductor material | Lower irradiance levels and potential power absorption instead of production |
How is solar panel degradation measured?
Physical inspection on-site is the most commonly used method to measure solar panel degradation.
The output of a working solar panel is measured from time to time for a specific period and the rate is computed based on an expected value.
In 2018, 2 researchers proposed a machine-based method of real-time solar panel inspection, meant to be:
- Time conscious
- Cost-effective, and
- Safer due to reduced contact and hence a reduction in damage of solar panels.
If adopted, the method could revolutionize solar panel degradation inspection and computations.
Solar panel degradation is expressed as an expected rate, usually a percentage. The degradation rate gives consumers an idea of the time at or below which a solar panel’s output will decrease by a certain margin.
Most solar panel manufacturers indicate a 1% degradation rate per year on the solar panels.
However, according to a study by the National Renewable Energy Laboratory, most monocrystalline panels made after the year 2000 degrade at an average rate of 0.4%.
This shows that what manufacturers set as the degradation rate is not always how the individual solar panels will perform in real life.
Here’s what the typical solar panel’s output would look like over a period of 30 years for both the 0.4 and 1% degradation rates.
| Year | For 0.4% degradation rate | For 1% degradation rate |
| 5 | 98 | 95 |
| `10 | 96 | 90 |
| 15 | 94 | 86 |
| 20 | 92 | 81 |
| 25 | 90 | 77 |
| 30 | 88 | 73 |
Looking at these figures, it’s evident that:
- The degradation rate has a significant effect on a solar system's output.
- A slight difference in the degradation rate leads to a substantial change in the production of solar panels.
Solar panel degradation rate comparison
Why do solar panels degrade?
Now let’s discuss the primary causes of solar panel degradation.
1. Poor handling
Whether it’s during installation or maintenance of the solar panels, improver handling can stress the solar panels leading to degradation.
If, for example, during cleaning of the solar panels, water is let to seep in, corrosion and eventually performance problems will arise.
Expert tip: Hire experienced people to install and properly maintain your solar panels.
2. The UV rays of the sun
Surprisingly, the sun, which is supposed to keep solar panels ‘alive’, can degrade them.
The sun’s UV rays hit hard on solar panels and cause high degradation in a very short time. This form of solar panel degradation is called light-induced degradation.
LID is always at its peak right after installation, when the solar panels are exposed to the sun for the first time. It, however, slows down over time.
Expert tip: Invest in solar panels doped or crafted with reliable UV blockers.
3. Extreme weather events
Weather events such as strong winds and heavy snowfall caused flexing and cracking in solar panels.
This can be a real threat to your solar panel’s longevity. Preventing the degradation of solar panels by adverse weather conditions is entirely something under your control, as advised below.
Expert tips:
- Ensure you buy high-quality solar panels- Premium quality solar panels have sturdy components that can withstand bad weather.
- Make sure the panels are strategically installed. If, for example, your solar panels are installed in an area with wind blowing trees, they’ll definitely suffer the damage. Always work with reliable experts who can strategically install your solar panels.
4. Extreme temperatures
Too hot or too cold weather conditions also contribute to solar panel degradation.
When the temperatures are too high, the panels expand and when it’s too cold, they contract. With continued expansion and contraction of the solar panels (thermal cycle), microcracks may form, causing degradation in the long run.
Expert tip: The weather is quite hard to control, so you may want to be a little more focused on the quality of the solar panel you buy. Let’s briefly discuss this below.
Manufacturing quality and solar panel degradation
While solar panel degradation may be inevitable, good-quality solar panels will always have low degradation rates.
This gives you an assurance that the solar system’s performance won’t be affected significantly over the course of the panel’s lifetime.
By investing in high-quality solar panels, you’re assured that they’ll maintain their production capacity in the long run.
Regardless of your budget, you should never settle for poor-quality solar panels, as they’ll end up hurting you in the long run.
Solar panel efficiency
The production capability of solar panels goes hand in hand with efficiency.
What is solar panel efficiency?
Solar panel efficiency (also called conversion efficiency) is the measure of the amount of sunlight that’s converted to electricity by a solar panel. The average conversion efficiency of most solar panels is 15-20%.
Calculating solar panel efficiency (%)
Efficiency= (Pmax)/ (Area×1000W/m2) ×100
Pmax- Maximum power rating of the solar panel in Watts
1000- Solar irradiance at Standard Test Conditions in W/m2
m2- Surface area of the solar panel in square meters
Key factors determining solar panel efficiency include:
- Cell type
- Interconnection of the cells
- Irradiance level
- Temperature
The solar cell type is the primary factor that affects solar panel conversion efficiency. Here’s an outline of solar cell types and their average efficiency:
| Solar cell panel type | Efficiency |
| N-type IBC | 20-23% |
| Half-cut MBB Heterojunction | 20-22% |
| Shingled Mono-PERC Half-cut Mono PERC MBB | 19-20.5% |
| Half-cut Mono PERC Shingled Mono Cells | 18-20% |
| Mono PERC | 17-19% |
| Poly PERC | 16-17% |
KEY:
IBC- Interdigitated Back Contact
PERC- Passivated Emitter and Rear Contact
MBB- Multi-busbar/Multiwire
Brands such as Sunpower, LG, REC, and Panasonic lead when it comes to producing high-efficiency solar panels.
To get real value for your money, go for solar panels with high efficiency so that they serve you optimally during their useful life.
Tip: Since it’s unlikely that you’ll replace the solar panels before their life is over, you can boost the system's capacity anytime you feel like it’s not meeting your energy needs.
What are solar panels performance warranties?
A solar panel’s performance warranty is a guarantee by a manufacturer to the consumer that the solar panel will produce electricity at a certain percentage for a given period.
Solar panel manufacturers generally guarantee 90% production for the first 10 years and 80% for the lifetime (20-30 years) of the solar panel.
Here’s a point to note: Performance warranties are just conservative numbers that manufacturers set from their speculations.
The experience is different in real life, and in most cases, solar panels outperform these speculations. In this regard, you can view the numbers as upper limits for the anticipated degradation.
How long do solar panel batteries last?
Solar panel batteries last 3-10 years, depending on the brand. Clearly, this is a short lifespan (and it can get lower), so you need to be a little more focused on their maintenance.
Here are some tips you can consider:
- Ensure that your solar panels are installed properly and that their capacity is well catered for.
- Inspect them properly to ensure that everything is intact and working properly.
- If you’re using lead-acid batteries, ensure they’re fully recharged after use or before you put them into use again.
What’s the lifespan of my inverters?
Other than the batteries, the solar panels are the other major components of the system that you’ll have to replace before the panels' lifetime is over. Grid-tier inverters will last around 10 years, while off-grid inverters will last 5-10 years.
Always remember that no matter the kind of system you have, you’ll need to replace the inverters at least once before the panel’s lifespan is over.
For extended warranty deals, you should buy your inverters direct from manufacturers.
What's the difference between product warranty and performance warranty of solar panels?
A product warranty is a guarantee covering a solar panel’s premature failure. This may be due to defects in the manufacturing process.
On the other hand, a performance warranty is a guarantee that a solar panel will generate a given amount of power for a certain period of time.
Conclusion
Outdoor elements such as UV rays of the sun, strong winds, extreme temperatures are the leading causes of solar panel degradation.
The degradation is high shortly after installation, mainly due to LID, but it reduces significantly over the rest of the solar panel’s lifetime.
To reduce the rate of solar panels degradation, you must ensure that first, they’re of high quality when buying them. Next, you must ensure that they’re strategically and properly installed.
Lastly, you need to do frequent checks and proper cleaning of the solar panels to maintain their pristine conditions for a long time.
Yes, solar is supposed to be a maintenance free-investment, but regular maintenance can help extend their lifespan, despite their inevitable degradation.
