Solar Panel Degradation: How Much Power You Lose Over 25 Years

When homeowners hear their solar panels will "degrade" over time, they often picture dramatic performance drops and disappointing savings. The reality is much more reassuring: modern solar panels are among the most durable energy-producing assets you can buy. According to the National Renewable Energy Laboratory (NREL), today's panels typically lose only about 0.5% of their output per year — meaning a 25-year-old system still generates roughly 87% of its original power.

But understanding how degradation works, what affects it, and how warranties protect you is essential before you sign a 25-year contract. Here's what you actually need to know.

What Is Solar Panel Degradation?

Solar panel degradation refers to the gradual decline in power output over the panel's lifetime. It's caused by a mix of factors — UV exposure, thermal cycling, humidity intrusion, and microscopic cracks in silicon cells — that slowly reduce how efficiently sunlight is converted to electricity.

NREL's landmark study of nearly 2,000 degradation measurements found a median degradation rate of 0.5% per year for modern crystalline silicon panels installed after 2000, according to their Photovoltaic Degradation Rates analysis. Older panels from the 1980s and 1990s degraded faster — closer to 0.8–1.0% per year — but manufacturing improvements have dramatically slowed the process.

The Two Types of Degradation

Not all degradation is equal. There are essentially two phases:

• Light-Induced Degradation (LID): A one-time drop of 1–3% that happens during the first few hundred hours of sun exposure as the silicon stabilizes. This is baked into manufacturer specifications.
• Long-term degradation: The slow, steady ~0.5% annual decline that continues throughout the panel's life.

When you read "25-year performance warranty at 87%," manufacturers have already accounted for LID in that number.

How Much Power Do You Actually Lose?

Let's translate 0.5% per year into real numbers. Say you install a 10 kW system that produces 14,000 kWh in year one.

• Year 5: ~13,650 kWh (97.5% of original)
• Year 10: ~13,300 kWh (95% of original)
• Year 15: ~12,960 kWh (92.5% of original)
• Year 20: ~12,635 kWh (90% of original)
• Year 25: ~12,320 kWh (87.8% of original)

Here's the good news: electricity rates historically rise faster than panels degrade. The U.S. Energy Information Administration (EIA) reports residential electricity prices have climbed roughly 2.5% per year on average over the past two decades. So while your panels produce slightly less each year, the value of each kWh you offset keeps rising — often outpacing the degradation curve entirely.

What Warranties Actually Promise

Every reputable solar manufacturer offers a performance warranty separate from the product (equipment) warranty. Here's how to read one:

• Product/equipment warranty: Covers manufacturing defects. Typically 12–25 years, with premium brands (SunPower/Maxeon, REC, Panasonic, Qcells Q.PEAK) offering 25+ years.
• Performance warranty: Guarantees minimum output over time. A standard warranty promises at least 80–85% of rated power at year 25. Premium panels guarantee 90–92%.

According to EnergySage's warranty guide, the industry has shifted noticeably toward 25-year product warranties across both tiers in the last five years — a strong signal that manufacturers trust their own durability data.

What Triggers a Warranty Claim

If your panels produce less than the warrantied percentage at any checkpoint year, the manufacturer is obligated to repair, replace, or compensate you. In practice, this requires:

1. A monitoring record showing underproduction
2. A technician's report confirming the issue isn't caused by shading, soiling, or inverter failure
3. Documentation proving the panels were installed by a certified professional

This is one reason why choosing a reputable installer matters more than chasing the lowest bid — bad workmanship can void the warranty. You can compare vetted installers through EnergyScout's installer directory.

What Makes Panels Degrade Faster?

While 0.5% per year is the median, real-world degradation varies. Factors that accelerate decline include:

1. Heat

Solar panels are tested at 25°C (77°F), but a rooftop panel can easily hit 65°C (149°F). NREL research shows that for every 10°C increase in operating temperature, degradation accelerates measurably. Panels in Phoenix degrade faster than panels in Seattle.

2. Humidity and Salt Air

Moisture penetration is a leading cause of cell cracking and corrosion. Coastal installations or homes in humid climates (Florida, Gulf Coast) can see slightly higher degradation unless panels are rated for those conditions.

3. Microcracks from Installation

Rough handling during shipping or installation can create invisible microcracks that grow over years of thermal cycling. The Solar Energy Industries Association (SEIA) emphasizes that installer quality is one of the biggest predictors of long-term performance.

4. Snow, Wind, and Hail

Extreme weather events can cause sudden damage — not just gradual degradation. Most homeowners policies cover this, but verify coverage before you sign.

Monitoring Your System's Actual Degradation

Nearly every modern solar system includes production monitoring through the inverter manufacturer's app (Enphase Enlighten, SolarEdge Monitoring, Tesla Gateway, etc.). To track degradation:

1. Record your first full year's production as a baseline.
2. Compare each subsequent year's output, normalized for weather (most apps do this automatically).
3. If annual decline exceeds 1% without clear cause (shading, soiling, failed microinverter), file a warranty inquiry.

A Lawrence Berkeley National Laboratory analysis of residential systems found that most households dramatically underutilize their monitoring tools — missing early warning signs of inverter failures that look like accelerated degradation but are actually fixable problems.

Should Degradation Change Your Purchase Decision?

In a word: barely. Here's why:

• Payback still happens fast. Even accounting for degradation, most U.S. systems break even at years 7–12, leaving 13–18 years of nearly free electricity.
• Premium panels aren't always worth it. A Tier-1 panel at 0.55% degradation costs less upfront than a premium panel at 0.25% degradation. Over 25 years, the premium panel produces only ~3–5% more energy — rarely enough to justify a 15–25% price premium.
• Workmanship matters more than specs. A sloppy installation of premium panels will degrade faster than a professional installation of standard panels.

What About After 25 Years?

Panels don't suddenly stop working at year 25 — that's simply when most warranties end. Real-world studies from the U.S. Department of Energy's Solar Energy Technologies Office show many panels from the 1980s and 1990s still operating at 75–80% output after 30–40 years. You may choose to replace them for efficiency gains or simply let them continue producing free power.

When replacement does make sense, check whether your state has solar incentives for repowering. Our incentive search tool tracks state-level solar and battery rebates by ZIP code.

One Important Note on Federal Tax Credits

If you're weighing a new solar system, know that the federal 30% Investment Tax Credit for purchased residential systems expired in 2026. Only solar leases and PPAs (third-party-owned systems) still qualify for federal credits that flow through to lower lease payments. State and utility incentives, net metering, and bill savings remain the main financial drivers for purchased systems.

Bottom Line

Solar panel degradation is real but remarkably slow — and remarkably predictable. A quality modern system will produce 85–90% of its original output after 25 years, and electricity rate inflation typically offsets that decline in dollar terms. The bigger levers on your long-term performance aren't the panels themselves but your installer's quality, your monitoring habits, and your warranty paperwork.

Want to see what a solar-plus-battery system would produce — and save — at your home? Take the free EnergyScout assessment to get a degradation-adjusted savings estimate, compare vetted installers, and access every current incentive in your ZIP code.