When homeowners think about going solar, one of the big questions is: How long will my solar panels last? While panels are built to last decades, they do experience a natural, gradual decline in performance called degradation rate.
In simple terms, the degradation rate is the percentage of power output a solar panel loses each year as it ages. It doesn’t mean your panels suddenly stop working after 20–30 years — far from it. Instead, they just produce slightly less energy each year compared to when they were brand new.
In this guide, we’ll break down everything you need to know about solar panel degradation:
- A simple explanation anyone can understand.
- The science behind why it happens.
- How degradation is measured.
- Real-world examples of how it affects homeowners.
- Which solar panels have higher or lower degradation rates.
- How manufacturers design panels to slow it down.
- Tips for choosing panels with the lowest degradation.
By the end, you’ll have a clear picture of what degradation really means for your solar investment.
The Simple Explanation
Every year, solar panels lose a small percentage of their ability to turn sunlight into electricity. On average, modern solar panels degrade at about 0.3%–0.6% per year.
That means if a new panel produces 100% of its rated power on day one:
- After 10 years, it might produce around 95%.
- After 25 years, it might produce around 88–92%.
- After 30 years, it might still be producing 85–90% of its original output.
This slow, predictable decline is factored into warranties and financial estimates, so your expected savings already account for it.
Why Do Solar Panels Degrade?
Degradation happens because solar panels are constantly exposed to the elements — sunlight, heat, cold, moisture, and electrical stress. Over time, those conditions wear down the materials. Here are the main causes:
1. Light-Induced Degradation (LID)
Some types of solar cells lose a little performance in the first few weeks of sun exposure. This is a one-time drop that stabilizes quickly.
2. Heat and Light Stress
High temperatures combined with constant sunlight can slowly change the structure of silicon cells, leading to reduced efficiency.
3. Potential-Induced Degradation (PID)
High electrical voltage differences inside a panel can cause energy to leak through the materials, reducing performance.
4. Moisture and Weathering
Even sealed panels can slowly let in small amounts of moisture, which can corrode connections or cloud encapsulants.
5. Mechanical Stress
Wind, snow, and even the expansion and contraction of materials through hot and cold cycles can create micro-cracks in cells. These tiny cracks don’t stop a panel from working, but they can reduce its overall output.
How Is Degradation Measured?
Degradation is measured as the percentage loss per year of a panel’s rated power. Manufacturers test this in both labs and real-world installations to estimate long-term performance.
When you look at a solar panel’s warranty, you’ll often see two parts:
- First-year degradation: Some panels allow for a slightly larger initial drop (usually 1–2%) due to light exposure.
- Annual degradation rate after year one: This is the consistent yearly decline, such as 0.25% or 0.5%.
By year 25, the warranty will guarantee a certain percentage of the panel’s original output. For example, a panel with a 0.5% annual degradation might be guaranteed to produce at least 88% of its original output after 25 years.
Why Degradation RATE Matters for Homeowners
The key takeaway is that degradation doesn’t mean your panels are failing — it just means they’re a little less powerful over time.
Impact on Energy Production
If your system was expected to produce 10,000 kWh in the first year, by year 25 it might produce 8,800–9,200 kWh depending on the degradation rate. You’ll still be making plenty of energy and saving money, just slightly less than in year one.
Financial Impact
Solar savings calculations already include conservative degradation estimates. A system that pays for itself in 8–10 years will still deliver strong savings over decades, even with normal degradation.
Home Value
Panels with lower degradation rates and stronger warranties can add to home value since they reassure future buyers that the system will still be producing well for many years to come.
Which Panels Degrade Less (and Which Degrade More)?
Not all solar panels age at the same rate. The type of solar cell technology makes a big difference.
- IBC (Interdigitated Back Contact, usually n-type): Some of the best degradation rates in the industry, with warranties extending up to 40 years and promising around 88% output even then.
- HJT (Heterojunction, n-type): Very low degradation, often warrantied at 0.25% per year, which equals about 92% output after 25 years.
- TOPCon (n-type): Newer technology that typically offers around 0.4% annual degradation, with some models extending warranties to 30 years.
- Mono PERC (p-type): Common and cost-effective, usually warrantied around 0.5% per year. Reliable, but more prone to light-induced effects.
- Older Polycrystalline panels: Historically degraded faster, often closer to 0.6–0.8% per year. Most new residential systems today use monocrystalline instead.
Example: How Degradation Adds Up
Let’s compare two panels, both starting at 400 watts:
- Panel A (0.5% per year):
- Year 25 = about 353 watts
- Retains 88% of original power
- Panel B (0.25% per year):
- Year 25 = about 368 watts
- Retains 92% of original power
The difference might not sound huge, but over 25 years the higher-quality panel can produce thousands more kilowatt-hours.
How Manufacturers Reduce Degradation
Panel makers use several design improvements to keep degradation as low as possible:
- Better cell types: N-type silicon cells resist light-induced degradation better than older p-type cells.
- Glass-glass construction: Using glass on both sides of the panel improves moisture resistance and mechanical strength.
- Improved encapsulants: Modern materials help prevent corrosion and potential-induced degradation.
- Quality testing: Panels go through international standards testing to ensure they can handle heat, cold, UV, and humidity stress.
Frequently Asked Questions
Do all panels degrade at the same rate?
No. Different technologies and materials degrade at different speeds. Premium panels often have lower degradation rates.
Can I stop degradation?
You can’t stop it completely — it’s part of the natural aging process. But you can slow it down by choosing high-quality panels and ensuring proper installation.
Do panels degrade faster in hot climates?
Yes, heat can accelerate certain degradation effects. That’s why lower temperature coefficient panels (like n-type) are popular in hot regions.
What’s the industry average?
Most modern panels degrade at 0.3%–0.6% per year, meaning they’ll still produce 85–92% of their original power after 25 years.
Does shading increase degradation?
Shading doesn’t directly cause faster material aging, but it can stress certain cells. Good system design and microinverters or optimizers help reduce this risk.
The Bottom Line
Degradation is normal, expected, and already factored into solar system performance estimates. The good news is that today’s solar panels are lasting longer and degrading more slowly than ever before.
- Average panels: 0.5% per year degradation → about 88% output after 25 years.
- Premium panels: 0.25% per year degradation → about 92% output after 25 years.
- Top warranties: Some now extend to 30–40 years, showing confidence in low degradation rates.
For homeowners, the key takeaway is this: Your panels won’t “die” after 25 years — they’ll still be producing strong, valuable energy. Choosing a panel with a lower degradation rate just means more energy and more savings over the long run.
