A solar panel installed today will not produce the same output in year twenty as it did on day one. That’s normal, and it isn’t a sign of a faulty system. It’s called degradation, and every panel on the market experiences it in some form.
The number that matters is how much it degrades each year and whether the installer chose panels and mounting conditions that keep that number low. Get that wrong and a system that looked good on paper can underperform its projected returns by a noticeable margin over 25 years.
What Is Solar Panel Degradation?
Solar panel degradation is the gradual drop in a panel’s power output caused by exposure to sunlight, heat, humidity, and mechanical stress over years of operation. The silicon cells, the encapsulant layer, the wiring, and the junction box all age slowly, and each contributes a small amount to the overall loss.
Manufacturers account for this in their warranties. A typical performance warranty guarantees around 90% of rated output at year 10 and 80–85% at year 25. That guarantee is built around an assumed curve, not a fixed number that applies to every panel everywhere.
How Fast Do Solar Panels Actually Degrade?
Field data collected by the US National Renewable Energy Laboratory (NREL) across tens of thousands of installed systems puts the median degradation rate at roughly 0.5% per year for modern crystalline modules, with an average closer to 0.8% once older and lower-quality panels are included. Panels from top-tier manufacturers, including premium monocrystalline and HJT modules, often stay under 0.35% a year.
That first year is usually the steepest drop. Most modules lose 1–3% of output within the first twelve months as the cells settle into a stable state, a process known as light-induced degradation. After that, the yearly loss slows down and tends to stay fairly consistent for the rest of the panel’s working life.
Here’s roughly what that looks like in practice for a system rated at 100% on day one:
- Year 5: 96–98.5% of original output, depending on panel quality
- Year 10: 92–96% of original output
- Year 20: 87–92% of original output
- Year 25: 84–90% of original output
The spread between the low and high end of these ranges is exactly why panel selection matters as much as panel count when a system is designed.
What Causes Solar Panels to Degrade Faster
Not every installation ages at the same rate. A handful of factors push degradation well past the industry median.
Heat and thermal cycling. Panels lose efficiency as cell temperature rises, and repeated heating and cooling stresses the solder joints and cell connections. Rooftop installations in Hyderabad, Vijayawada, and other high-ambient-temperature cities in Telangana and Andhra Pradesh see more thermal stress than installations in cooler regions, which is why proper ventilation gaps behind the panels matter during installation.
UV exposure and encapsulant discolouration. Years of direct sun exposure can yellow the EVA encapsulant layer that protects the cells, reducing the amount of light reaching the silicon. Lower-grade encapsulant materials discolour faster.
Humidity and moisture ingress. Moisture that gets past a weak backsheet or a poorly sealed junction box corrodes the internal circuitry. This is a bigger risk in coastal cities like Visakhapatnam, where humidity stays high for much of the year.
Potential-induced degradation (PID). A voltage difference between the cells and the grounded frame can cause current leakage, sometimes cutting output by 30% or more within a few years if left unaddressed. Panels with anti-PID coatings, and inverters configured correctly for the array’s grounding setup, largely prevent this.
Micro-cracks and physical stress. Hail, rough handling during transport, or poor mounting technique can crack cells in ways that aren’t visible from the ground but reduce output and speed up long-term decay.
Soiling and dust accumulation. Dust, pollen, and pollution buildup isn’t technically degradation since a clean can restore the loss, but in dry industrial areas it can mimic degradation symptoms if cleaning schedules are inconsistent. Industrial parks and factory rooftops typically need more frequent cleaning than residential rooftops.
How to Slow Down Solar Panel Degradation
A few decisions at the design and installation stage make a measurable difference over the life of a system.
Choose Tier-1 panels with documented degradation data. Ask for the manufacturer’s linear performance warranty, not just a headline efficiency number. A panel rated at 0.4% annual degradation will outperform one rated at 0.7% by a wide margin over 25 years, even if their day-one specs look identical.
Get the mounting and ventilation right. Panels need airflow underneath them to avoid excess heat buildup. This is a design detail that’s easy to skip during a rushed installation and expensive to fix afterward.
Match the inverter and grounding configuration to the panel technology. This is one of the simplest ways to prevent PID-related losses, and it costs nothing extra if it’s planned correctly from the start.
Set a realistic cleaning schedule. For commercial and industrial rooftops especially, a maintenance contract that includes periodic cleaning and visual inspection catches soiling losses and early-stage cell damage before they compound.
Monitor actual output against expected output. A monitoring system that flags when a string is underperforming lets you catch a failing panel or a wiring fault long before it shows up as a meaningful drop in your monthly generation numbers.
Why This Matters When You’re Evaluating a Solar Quote
Two proposals with the same panel count and the same headline wattage can deliver very different lifetime energy yields if one uses panels with a 0.3% degradation rate and the other uses panels closer to 0.8%. Over 25 years, that gap alone can be worth several percentage points of total generation, which translates directly into savings and payback period.
At Hydromo, panel selection for residential, commercial, and industrial installations across Telangana and Andhra Pradesh starts with documented degradation data, not just price per watt. Local heat, humidity, and dust get factored into mounting design and maintenance planning from day one, not bolted on afterward.
Not sure how your current system’s output compares to what it should be delivering? Request a Free Solar Assessment with Hydromo’s engineers and get a clear picture of your system’s actual performance against its expected degradation curve.
FAQ Section
Q: What is a good degradation rate for solar panels?
A: Anything at or below the NREL median of 0.5% per year is considered good. Premium panels from established manufacturers often guarantee 0.3–0.4% per year.
Q: Do solar panels stop working after 25 years?
A: No. The 25-year mark is a warranty milestone, not an expiry date. Most panels keep generating power well past 25 years, just at reduced output.
Q: Can solar panel degradation be reversed?
A: Degradation from aging materials can’t be reversed, but losses from dust, soiling, or a failing component can often be recovered through cleaning or repair.
Q: Does hot weather in Telangana and Andhra Pradesh affect degradation?
A: Yes. Higher ambient temperatures and thermal cycling can push degradation rates above the global median if the system isn’t designed with adequate airflow and heat-tolerant components.
Q: How do I check if my solar system is degrading faster than expected?
A: Compare your monthly generation data against the manufacturer’s expected output curve for your panel model. A consistent monitoring setup makes this comparison straightforward.