Solar Panel Degradation: What to Expect After 10, 15, and 25 Years

Last updated: February 2026

Solar panels don't break — they fade. Unlike a failed appliance or a blown fuse, solar panel degradation is silent and gradual, reducing your system's output by a small percentage each year over decades. Understanding this process is important both for evaluating your current system's performance and for making smart buying decisions when comparing panel brands and warranties.

The good news: modern solar panels degrade far more slowly than early-generation technology, and the best tier-1 manufacturers are backing their panels with performance guarantees that are increasingly meaningful.

Here's what the data actually shows about how solar panels age, what to expect at the 10-, 15-, and 25-year marks, and how degradation should factor into your payback calculations.

What Is Solar Panel Degradation?

Solar panel degradation refers to the gradual reduction in a panel's electricity output over time, expressed as a percentage per year. A panel with a 0.5%/year degradation rate that produces 400 watts when new will produce:

• 400W × (1 - 0.005)^10 = 381W after 10 years (95.1% of original)
• 400W × (1 - 0.005)^15 = 371W after 15 years (92.7% of original)
• 400W × (1 - 0.005)^25 = 352W after 25 years (88.0% of original)

At a 0.3%/year degradation rate (premium panel performance):

• 400W → 388W after 10 years (97.1%)
• 400W → 383W after 15 years (95.6%)
• 400W → 374W after 25 years (93.5%)

The difference between 0.5%/year and 0.3%/year compounds significantly: over 25 years, a premium panel produces 5.5% more cumulative energy than an average panel, on a per-watt basis. On a 10 kW system producing 14,000 kWh/year in year one, that's an additional 7,700 kWh over the system's lifetime — roughly $1,100 worth of electricity at a 14.5¢/kWh rate (EIA February 2026 national average).

NREL Data: What Real-World Degradation Rates Look Like

The National Renewable Energy Laboratory's most comprehensive study on solar panel degradation (Lawrence et al., updated 2023) analyzed over 40 years of field data across thousands of systems and found:

• Median degradation rate across all field systems: 0.50%/year
• Median for systems installed after 2010: 0.36%/year
• Range for most modern tier-1 panels: 0.25–0.60%/year
• Percentage of systems degrading faster than 1%/year: Less than 5%

The improvement in median degradation rate from older to newer systems reflects real advances in solar cell manufacturing: better silicon purity, improved encapsulant materials, more robust backsheets, and better anti-reflective coatings that resist yellowing and soiling.

Panel Technology and Degradation: What Makes a Difference

Not all solar panels degrade at the same rate. Technology type, cell efficiency, and manufacturer process quality all play significant roles.

Standard Monocrystalline PERC: 0.40–0.55%/year

Passivated Emitter and Rear Contact (PERC) monocrystalline cells are the dominant technology in 2026 for standard residential panels. Most major tier-1 brands — Jinko Solar, Canadian Solar, REC Group, Qcells — sell high-quality PERC panels with degradation rates in this range. They typically carry 25-year performance warranties guaranteeing 80–83% output retention.

TOPCon Technology: 0.25–0.35%/year

Tunnel Oxide Passivated Contact (TOPCon) cells represent the current state of the art for mainstream residential solar. Brands including Jinko Tiger Neo, Canadian Solar HiHero, Longi Hi-MO 6, and REC Alpha Pro use TOPCon architecture. These panels demonstrate lower degradation in field data and increasingly carry performance warranties of 85–87% at 25 years.

Maxeon (SunPower) Technology: 0.25%/year

SunPower's Maxeon cells have a unique all-back-contact architecture that eliminates front-side bus bars — the thin metal lines on standard panels that are a primary site for corrosion and degradation over time. The result is the lowest measured field degradation rate of any commercially available residential panel: 0.25%/year. SunPower's performance warranty is industry-leading at 92% output retention at 25 years.

Reading Solar Warranties: What Actually Matters

Solar panel manufacturers offer two distinct warranties:

1. Product (materials/workmanship) warranty: Typically 10–15 years. Covers defects in materials and manufacturing — delamination, junction box failures, cracked cells, etc. If a panel physically fails, this warranty pays for replacement.

2. Performance (power output) warranty: Typically 25–30 years. Guarantees that output won't fall below a specified percentage of rated power. This is the degradation guarantee.

The performance warranty is the critical one for long-term system economics, and the fine print matters:

Standard 80% at 25 years warranty: This means the manufacturer only has to replace or credit the panel if output falls below 80% of rated power at the 25-year mark. With typical 0.5%/year degradation, panels reach 87–88% at year 25 — well above the 80% floor. This warranty is rarely triggered even for poorly performing panels.

Better warranties (85–92% at 25 years): More meaningful because they establish a higher floor. A 92% at 25-year guarantee (SunPower) means the company is committed to near-original performance for 25 years — a meaningfully different commitment.

Step warranties: Some manufacturers structure their performance warranty as steps (e.g., 97% at year 1, 91.2% at year 10, 84.8% at year 25). Read each step, not just the final guarantee.

What to Expect at 10, 15, and 25 Years: Realistic Scenarios

10-Year Check

At year 10, a well-maintained standard residential solar system should produce 93–96% of its year-one output depending on panel quality. This is within normal range and doesn't indicate a problem unless production has dropped more than 7–8% per watt.

Your inverter is statistically more likely to need attention than your panels at the 10-year mark. String inverters (SMA, Fronius, SolarEdge) carry 10–12 year warranties and may need replacement or repair around year 10–15. Microinverters (Enphase IQ series) carry 25-year warranties and generally outlast string inverters in field reliability.

What to do at year 10: Pull your annual production data (available in your monitoring app) and compare to your original system estimate. If production has fallen more than 10% from the estimate, investigate the cause — shading from grown trees, panel soiling, inverter efficiency loss — before attributing it purely to panel degradation.

15-Year Mark

At year 15, expect 90–93% of original output (premium panels) or 87–90% (standard PERC). Your system is now producing measurably less than new, but still generating significant electricity and savings.

The key economics at year 15: solar panel prices have dropped dramatically since your original installation. A 10 kW system that cost $28,000 in 2026 may cost $15,000–18,000 to replicate in 2041 with equivalent efficiency panels. This makes full system replacement rarely worthwhile at year 15 unless there are significant panel defects or physical damage.

What to do at year 15: If production has dropped more than 15% below original estimates, get a professional solar site assessment. Isolate whether the issue is panels, inverter, wiring, or external factors before deciding on remediation.

25-Year Mark

At 25 years, standard panels produce 87–88% of original output; premium panels, 92–94%. The panels themselves are typically still functioning — solar panels don't "die" at 25 years; they just continue degrading. NREL field studies have documented functional panels from the 1990s still generating power in 2025 at reduced capacity.

However, other system components may be reaching end of life: the original string inverter has likely been replaced once already, racking hardware should be inspected for corrosion, and wiring insulation may need attention in harsher climates.

The 25-year decision: At this point, the economics of upgrading vs. continuing operation depend on panel prices at that time, your electricity rate, and available incentives. Given solar panel price trajectories, full system replacement at year 25 with new high-efficiency panels is likely economically compelling — essentially starting a fresh 25-year ROI cycle.

How Degradation Affects Your Payback Calculation

Degradation is built into all sophisticated solar payback calculations, but many online tools use oversimplified assumptions. Here's how to ensure your payback estimate is accurate:

Year-one production: Your installer should provide a production estimate based on your specific location's sun hours (from PVGIS or PVWatts), your roof's azimuth and tilt, and your system's specifications. This number is the starting baseline.

Annual degradation factor: Apply your panel's actual warranted degradation rate (or use 0.5% if unknown) to reduce production each year. Over 25 years, this compounds — your total energy production is approximately 89–92% of what you'd calculate using constant year-one output.

Electricity rate escalation: This works in the opposite direction — as rates increase (historically 2–3% per year), the value of each kWh you produce increases. This partially offsets the production decline from degradation.

Net effect: For most homeowners, the combination of degradation (~0.5%/year) and electricity rate escalation (~2.5%/year) means the financial value of your solar system actually increases slightly in real terms for many years before degradation eventually wins the tug-of-war.

Factors That Accelerate Degradation

Understanding what causes faster-than-normal degradation helps you protect your investment:

Heat: Chronically high operating temperatures accelerate degradation. Panels in Phoenix or Miami experience higher thermal cycling stress than those in Seattle or Boston. NREL data shows degradation rates in hot climates run approximately 15–20% higher than in temperate climates.

Humidity: High humidity environments increase potential for encapsulant delamination and corrosion of cell metallization. Coastal installations should use panels with moisture-resistant encapsulants.

Soiling: Accumulated dust, pollen, bird droppings, and other debris on panel surfaces reduce output (sometimes confused with degradation in monitoring data). Regular cleaning (or self-cleaning coating panels) prevents this masking effect.

Physical stress: Hail, heavy snow loads, and improper installation (incorrect torquing of mounting hardware) can cause microcracks in cells. These may not be immediately visible but cause localized cell failure over time.

Poor installation: Incorrect string sizing, reverse polarity connections, or inadequate waterproofing of junction boxes can cause accelerated degradation or outright failures. This argues for choosing reputable installers with strong track records.

The Bottom Line on Solar Panel Longevity

Modern tier-1 solar panels are genuinely durable products. The industry median degradation rate of 0.36%/year for post-2010 panels means a 10 kW system installed in 2026 will still be producing 91% of its original capacity in 2036 and 87% by 2051 — 25 years from now. That's a full quarter-century of meaningful electricity production from a product that, aside from occasional cleaning, requires essentially no maintenance.

The key takeaways:

• Budget for inverter replacement around year 12–15 (string inverters)
• Choose TOPCon or premium panel technology if long-term performance maximization is a priority
• Read performance warranties carefully — the guaranteed floor matters more than the marketing claim
• Degradation is normal; significant drops beyond the warranted rate should prompt investigation, not panic

Use the Solar Degradation Tracker below to model your specific system's production trajectory over time, and the Solar Payback Calculator to see how panel degradation is factored into your break-even analysis.

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Data sources: Jordan Lawrence et al., "Compendium of Photovoltaic Degradation Rates," Progress in Photovoltaics, NREL, 2023; NREL PVWatts Calculator; SunPower Maxeon Product Datasheet 2026; EnergySage Solar Panel Comparison Tool February 2026; EIA Electric Power Monthly February 2026