How much do solar panels degrade over time?

Most premium solar panels degrade at 0.5% per year, meaning a 400W panel produces about 390W after 5 years and around 350W after 25 years. Budget panels may degrade at 0.7–1% per year. Most manufacturers guarantee at least 80% of original output after 25 years, which reflects ~0.7% annual degradation.

Do solar panels last 25 years?

Yes — solar panels routinely last 25–35 years with minimal maintenance. The 25-year performance warranty most manufacturers offer guarantees at least 80–87% of original rated output. The panels don't 'stop working' at 25 years; they simply produce slightly less electricity over time and will continue operating past their warranty period.

How much do solar panels degrade each year?

Most modern solar panels degrade at 0.5–0.7% per year, as specified in manufacturer warranties. After 25 years at 0.5% annual degradation, panels produce about 88% of their original rated output. Premium panels (LG, Panasonic, SunPower) often degrade at 0.3–0.4% annually. Degradation accounts for the difference between year-1 and year-25 production.

Do cheap solar panels degrade faster?

Yes. Budget panels from lesser-known manufacturers often degrade at 0.8–1.0% per year or more. Over 25 years this compounds significantly — a panel degrading at 1%/year produces only 78% of original output by year 25, vs 88% for a 0.5% degradation rate panel. The production difference adds up to hundreds of dollars over the system's life.

Solar Panel Degradation Calculator

Calculate how your solar system's output declines over time due to panel degradation, and quantify the total production loss and dollar value reduction over a 25-year system lifetime.

Year-1 Output (kWh/yr)

Degradation Rate (%/yr)

Electricity Rate (¢/kWh)

Projection (years)

About This Calculator

Solar panel degradation is a slow but real reduction in output that every solar system experiences over its lifetime. Most tier-1 panels degrade at 0.3–0.7% per year, meaning a system producing 10,000 kWh in year one will produce roughly 8,800–9,300 kWh by year 25. Manufacturers typically guarantee that panels will produce at least 80% of rated output after 25 years — equivalent to a 0.87% annual degradation ceiling. This calculator shows you exactly what degradation means in kWh and dollars, helping you set realistic production expectations over the system's full life.

The difference between a 0.3% and 0.7% annual degradation rate might sound small, but it compounds meaningfully over 25 years. At 0.3%, year-25 output is 93% of year-one output. At 0.7%, it drops to 84%. Over the full 25 years, the higher-degradation system produces about 4–5% less total energy — which on a 10,000 kWh/yr system at $0.14/kWh translates to roughly $700–$1,000 in cumulative lost value. Premium panels with better degradation guarantees are often worth the small price premium for this reason, especially on large systems.

Actual degradation rates depend on panel chemistry and quality, climate (high temperatures accelerate degradation), and installation quality. Monocrystalline PERC panels typically degrade at 0.3–0.5%/yr; polycrystalline panels at 0.5–0.7%/yr; thin-film at 0.5–1.0%/yr. Your installer should specify the manufacturer's annual degradation guarantee in the performance warranty — look for this number explicitly in the warranty document, not just the 80% at-25-years guarantee, which obscures year-by-year performance expectations.

Degradation matters most when comparing competing proposals with different panel brands. A proposal using panels with a 0.25%/yr degradation guarantee will produce meaningfully more energy over 25 years than one with 0.7%/yr. This calculator lets you quantify that difference in kWh and dollars, turning a marketing claim into a concrete financial comparison you can use in your purchasing decision.

Calculations based on NREL solar modeling data and industry-standard assumptions, built and maintained by the independent SolarToolsOnline research team.

Estimates only — not financial, tax, or legal advice. Verify important results with a licensed solar installer or financial professional before making decisions.