Solar Panel Degradation Rate: A 2025 Guide (What to Expect)

Do you not know that solar panels deteriorate as time goes on? If not, think about it. People can read how solar panels have a life of 25 years or more, but not all of them are aware that the power output of solar panels reduces over the years. This gradual and constant reduction is referred to as the solar panel degradation rate. 

Degradation does not imply that your solar panels will break down. It means that as they grow older and as they are exposed to weather, they will produce a little less power annually than when they were new. Knowing this rate enables you to plan better how to produce a lot of energy and save in the long run.

What Solar Panel Degradation Means

Imagine solar panels as human bodies. They are energetic and do their best when they are new. They can work well even at an old age, only that they may not be as strong as they were before.

Each of the solar panels consists of silicon solar cells. These cells convert the sun’s rays into electricity. With time, these cells are damaged in a minor way by sunlight, heat, and other environmental factors. 

The materials become old, the links become rusted, and the covering becomes weak. All these micro effects cumulate, and you end up with a gradual decline in the quantity of electricity produced in your system every year.

This loss is normal. It’s also quite small compared to other technologies. Even after decades, solar panels remain reliable and productive.

How Solar Degradation Is Measured?

The solar panel degradation rate is calculated by the difference between the amount of power the panel currently generates and the amount it generated when new.

Standard Test Conditions (STC) is a testing of panels under controlled laboratory conditions by the manufacturer. These are tests that determine the efficiency of the panel in converting sunlight to electricity. After fitting, panels are usually retested a few years later to determine how their performance in the real world lives up to the first test findings.

When a panel that used to generate 300 watts now generates only 294 watts, it has settled down to 2% solar panel degradation rate. Then, the engineers measure an annual rate of depreciation by dividing the loss by the years in operation.

The general quality of panels available today degrades between 0.3 and 0.8 percent per year. That might sound small, but over 25 years it adds up — though the panels will still work well and save you plenty of money.

Annual Solar Efficiency Loss Rate 

In order to simplify this, we consider a simple example. Suppose your panel misses 0.6% of its energy each year.

Year	Estimated Power Output (%)	Total Power Lost (%)
1	99.4	0.6
5	97.0	3.0
10	94.1	5.9
15	91.4	8.6
20	88.8	11.2
25	86.3	13.7

As you may see, it will take 25 years before your solar panels will be able to generate less than 86% of the power they had when they were new. That is a great track record with regard to equipment that is exposed to sun, rain, and wind daily.

This gradual drop is what experts call solar efficiency loss. It’s slow, predictable, and already factored into most energy savings calculations when you buy your system.

Why Solar Panels Degrade?

Here are some factors that make solar panels degrade over time.

• Natural & Environmental Exposure

The solar panels are made in such a way that they handle the sunlight, but UV rays damage the protective coating. It is known as solar wear & tear, and all exterior materials give in to it as it progresses in time.

Heat also plays a big role. During hot weather, the materials swell a bit, and during cold weather, they contract. With thousands of heating and cooling processes, the solar cells may develop small cracks. Such microcracks are capable of diminishing the efficiency of the movement of electricity by the cells.

• Humidity In Weather

If the panels are sealed properly, still, moisture can creep and cause yearly solar output loss. It can either corrode electrical contacts or expand the layers inside. A minimal stagnant water can result in a gradual yet significant power outage.

• Dirt & Dust

Solar panels are covered by dust and pollen as well as pollution particles. Unless they are regularly cleaned, they will prevent the sunlight and lower performance. This accumulation may lead to heat stress with time, leading to degradation.

• Manufacturing Quality

The panels that are better are slower to degrade as they are constructed using strong materials. Reputable brands employ silicon of high purity and a powerful anti-reflective coating. Less expensive panels can deteriorate sooner due to lower-quality construction and lower-cost elements.

• Installation Quality

The improper installation may lead to premature solar panel degradation rate as well. When the mounting is not set flat or the wiring is not covered, the system may overheat or be exposed to water. When using professional installers, you must use those who have a good experience with your local climate.

Annual Solar Panel Degradation Rate & Energy Savings

The amount of power lost annually in the solar panels is minimal, and it does not have a significant impact on the saving of energy savings. Although the efficiency of solar panel performance declines slightly on a yearly basis, the overall production fluctuation is insignificant. The majority of systems remain powerful for many years.

Since the drop is not fast, it does not prevent you from saving money. These panels continue to generate electricity that is sufficient to reduce the energy bills even after installation. The majority of the homeowners break even in years and decades, and they are still enjoying their system.

Despite the penalty in terms of natural annual solar production, solar panels can be considered a sustainable and affordable means of reducing power bills. 

This gradual loss of efficiency is known as degradation. Decades of research from the National Renewable Energy Laboratory (NREL) show that modern, high-quality panels typically degrade at a rate of 0.5% to 1% per year.

How to Slow Down Solar Degradation

You cannot prevent the aging of panels, but you can delay it through routine maintenance.

• Cleanse dust and dirt occasionally.
• Shade your panels; keep off the branches.
• Watch for cracks or faded spots.
• Use the system app to see daily energy levels.
• Get a technician to check them every few years.

Conclusion

Degradation sounds technical, but it’s really simple — it’s just aging. Like any machine, solar panels lose a bit of their strength each year, termed as solar panel degradation rate. The positive aspect is that the rate is very low.

Your panels will generate 85 -90% of their original power after 25 years. It is amazing, especially when it comes to considering they work day in and day out, rain or shine.

If you take care of them and choose good equipment, solar energy will keep rewarding you for decades — both in savings and in clean power.

Looking for solar maintenance services to delay system degradation? Contact NEDES.US for worthwhile solutions!

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