How Fast Do Solar Panels Degrade?
The NREL degradation study — covering thousands of installations — found the median rate is 0.5% per year. A 400 W panel today will produce approximately 351 W after 25 years (87.8% of original).
Premium manufacturers like Maxeon and REC Alphaguarantee ≤0.25%/yr degradation. Over 25 years, their panels retain 93.8% vs. 87.5% for standard panels. On an 8 kW system, that difference adds up to roughly 8,200 additional kWh over the system's life — worth ~$1,150 at 14¢/kWh.
Top Solar Panel Warranties Compared (2026)
| Brand | Product Warranty | Performance Warranty | Degradation/yr | Yr 25 Output |
|---|---|---|---|---|
| Maxeon (SunPower) | 40 years | 40 years | ≤0.25% | 92% |
| REC Alpha | 25 years | 25 years | ≤0.25% | 92% |
| Panasonic EverVolt | 25 years | 25 years | ≤0.26% | 92% |
| Q CELLS Q.PEAK | 25 years | 25 years | ≤0.54% | 86% |
| LONGi Hi-MO 6 | 25 years | 25 years | ≤0.40% | 88% |
| Jinko Tiger Neo | 12 years | 25 years | ≤0.40% | 87.4% |
| Canadian Solar | 12 years | 25 years | ≤0.55% | 84.8% |
Source: Manufacturer datasheets, April 2026. Verify current warranty terms directly with manufacturer before purchase.
Inverter Lifespan: The Component Most Likely to Need Replacement
Solar panels rarely fail before 25 years. Inverters are the weak link.String inverters last 10–15 years on average — plan for one replacement during the system's life. Microinverters (Enphase IQ8) match panel lifespan at 25 years.
| Inverter Type | Expected Lifespan | Warranty | Replacement Cost | Best For |
|---|---|---|---|---|
| String inverter (SMA, Fronius) | 10–15 yrs | 10–12 yrs | $1,500–$3,000 | Simple unshaded roofs |
| Power optimizers + inverter (SolarEdge) | 12–20 yrs | 12 yrs | $1,200–$2,500 | Partial shade, monitoring |
| Microinverters (Enphase IQ8) | 25+ yrs | 25 yrs | Rarely needed | Complex roofs, shade |
25-Year Financial Impact of Panel Degradation
| Year | Standard (0.5%/yr) | Premium (0.25%/yr) | Output Diff (8 kW system) |
|---|---|---|---|
| Year 1 | 100% | 100% | — |
| Year 5 | 97.5% | 98.8% | +170 kWh/yr |
| Year 10 | 95.1% | 97.5% | +312 kWh/yr |
| Year 15 | 92.8% | 96.3% | +456 kWh/yr |
| Year 20 | 90.5% | 95.1% | +598 kWh/yr |
| Year 25 | 87.8% | 93.9% | +793 kWh/yr |
Based on 8 kW system, 10,400 kWh in year 1. 25-yr cumulative difference: ~8,200 kWh ≈ $1,148 at 14¢/kWh. Source: NREL degradation study.
What Warranties Cover — and What They Don't
The product/equipment warranty covers physical defects: delamination, cell cracking, frame corrosion, and junction box failures. Standard is 12 years; premium brands offer 25–40 years.
The performance warranty guarantees minimum output — typically 90% at year 10 and 80%+ at year 25. If your panels produce below threshold, the manufacturer replaces or compensates.
The installer workmanship warranty covers installation defects: roof leaks from improper flashing, loose connections, electrical faults. Standard is 5–10 years. If your installer goes out of business, this warranty becomes worthless — another reason to prefer established local companies. The US DOE solar homeowner guide recommends keeping all warranty documentation throughout the system's life.
Frequently Asked Questions
How long do solar panels last?
What is the difference between a product warranty and a performance warranty?
How fast do solar panels degrade?
How long do solar inverters last?
What happens if a panel fails under warranty?
Key sources:
• NREL — Photovoltaic Degradation Rates: An Analytical Review (Jordan & Kurtz)
Calculate Your 25-Year Solar Return
Our free calculator factors in degradation over time and gives you a realistic 25-year savings estimate based on real PVGIS data for your city.