Solar panel lifespan and degradation: what the real-world data shows
Panels installed in the 1980s are still producing electricity today. Field data contradicts the received wisdom that a solar panel “only lasts 25 years”. Here is what the NREL, Sandia and Hespul studies and French real-world experience actually say.
- →Panels installed in the 1980s–1990s still produce 70 to 75% of their initial output after 35–40 years. A Hespul (2024) study of 1992 panels shows they retain 79.5% of their output after 31 years.
- →The NREL analysed more than 54,000 systems: median degradation rate of 0.5%/year. Modern TOPCon and HJT technologies do better (0.25–0.45%/year).
- →The central inverter is the most vulnerable component: 12–20 years of service life versus 20–25 years for microinverters and 30–40 years for panels.
- →Over 25 years, the degradation gap between TOPCon and PERC amounts to about 15,000 additional kWh on 6 kWp, or ~3,000 € in additional savings.
- →In 2026, TOPCon has become the sensible default choice for residential use. HJT is justified on small surfaces, in hot areas or where maximum performance is required.
Lifespan of an installation's components
When we talk about the lifespan of a solar installation, the lifespan of the panels is often confused with that of the whole system. In reality, the components have very different life expectancies, and it is the central inverter that is the weak link.
Indicative lifespans, which vary with technology and conditions of use.
| Component | Warranty period | Estimated real lifespan | Note |
|---|---|---|---|
| Solar panels | 12-30 years | 30-40 years | Field studies consistently exceed warranties. Example: 1992 panels at 79.5% after 31 years. |
| Central inverter | 10-12 years | 12-20 years | 1 to 2 replacements expected over 30 years. |
| Microinverter | 12-25 years | 20-25 years | Lifespan close to that of the panels, but shorter. |
| LFP battery | 10 years | 15-20 years | 6,000-10,000 cycles → ~17 years at 0.6 cycles/day |
| DC cabling | Not specified | 25-30 years | UV-resistant sheathing mandatory on roofs |
| Mounting structure/fixings | Not specified | 30-40 years | A2 or A4 stainless steel required for long service life |
What the field data shows
The US laboratory NREL analysed more than 54,000 photovoltaic systems worldwide. Its main conclusion: the median degradation rate is 0.5%/year, and panels retain 85 to 90% of their initial output after 25 years of use.
In France, the association Hespul tested panels installed in 1992 (the Phébus 1 plant): after 31 years, they still produce 79.5% of their initial output. An earlier study (2013) of the same panels showed 91.7% of output after 20 years, confirming a non-linear and very slow degradation over the long term.
In the United States, Sandia National Laboratories has been monitoring installations since the 1980s: the oldest systems show 70 to 75% of their initial output after 35 to 40 years (Sandia data).
Why panels degrade: the 5 mechanisms
1. LID: Light-Induced Degradation
LID is an initial degradation that occurs during the first hours of exposure to light. It is caused by the formation of boron-oxygen complexes in P-type cells (PERC), an irreversible chemical reaction causing a power loss of 1 to 2% from the first year. N-type TOPCon panels have reduced this phenomenon (LeTID reduced to ~1.5%); HJT has eliminated it structurally.
2. LeTID: Light and elevated Temperature Induced Degradation
LeTID mainly affects PERC panels in conditions of high cumulative heat. Absent from N-type TOPCon and HJT panels, it helps explain why installations in very sunny areas (PACA, Occitanie) degrade faster with older PERC than with modern technologies.
3. PID: Potential-Induced Degradation
PID is caused by current leakage due to the voltage between the cells and the earthed frame. Today it is well under control thanks to high-resistivity EVA encapsulants and modern inverters that handle earthing properly. Require a PID-resistant certification on any panel bought in 2026.
4. Delamination
Delamination is the peeling of the encapsulant between the cells and the glass. It results either from poor manufacturing quality (insufficient encapsulant, faulty lamination process) or from mechanical impact. Visible to the naked eye as bubbles or discoloured areas, it is covered by the product warranty.
5. Mechanical ageing
Cyclical thermal expansion (a panel goes from -10 °C at night to +70 °C in summer) puts progressive mechanical stress on the seals, cell connections and cables. This ageing is inherent to outdoor use and explains why real-world lifespan varies with climate. Areas with a large temperature range (mountains, continental climate) age faster.
Degradation rates by technology in 2026
| Technology | Year-1 degr. | Annual degr. | Output at 25 years | 2026 status |
|---|---|---|---|---|
| Polycrystalline PERC | 2–3 % | 0.7–1%/year | ~78 % | Do not install any more |
| Monocrystalline PERC | ~2 % | 0.55–0.65%/year | 80–82 % | Declining |
| N-type TOPCon | ~1.5% | 0.35–0.45%/year | 87–89 % | 2026 standard |
| HJT heterojunction | ~1 % | 0.25–0.35%/year | 90–92 % | High end |
Indicative modelling, NREL data + manufacturers' data. Year-1 degradation is included in the curves.
N-type TOPCon accounts for more than 70% of new N-type residential installations in 2025–2026. Its extra cost over PERC has become marginal, while the gain over 25 years is significant. HJT stands out with a temperature coefficient of -0.24 to -0.26%/°C, the best on the market, which makes it particularly advantageous in hot regions.
Real impact on your financial return: the calculation by technology
For a 6 kWp installation producing 7,800 kWh in the first year, the difference in degradation between technologies translates into concrete savings over 25 years:
| Technology | Year-1 output | Year-25 output | Gap vs PERC | Gap in € (0.2001 €/kWh) |
|---|---|---|---|---|
| PERC (ref.) | 7,800 kWh | ~6,480 kWh | — | — |
| TOPCon | 7,800 kWh | ~7,090 kWh | +15,000 kWh | +3,000 € |
| HJT | 7,800 kWh | ~7,020 kWh | +18,200 kWh | +3,640 € |
Note: The values for PERC and HJT have been adjusted to reflect a residual output of 80–82% (PERC) and 90% (HJT) at 25 years, in line with data from NREL (2025) and REC (2026).
These calculations do not include the gradual rise in electricity prices (3%/year in our model). In reality, the advantage of low-degradation technologies grows over time, because each additional kWh is valued at a rising price.
How to choose in practice in 2026
Monocrystalline PERC is no longer the right choice in 2026: the extra cost of TOPCon has become marginal and the gain over 25 years is significant. Polycrystalline PERC should no longer be installed at all in residential settings.
Tight budget or standard project: choose N-type TOPCon.
- Product warranty: 12–15 years (e.g. LONGi.
- Performance warranty: 25–30 years (87–89% at 25 years).
- Degradation: ~0.40%/year (NREL).
- Fully compatible with 2026 hybrid inverters.
Small roof or very hot area: HJT is justified by its higher power density and its temperature coefficient of -0.24%/°C to -0.26%/°C . Example brands:
- Aiko Solar (world's leading HJT maker).
- REC Alpha Pure (the reference in France).
Long-term project or maximum performance requirements: HJT, with 0.25–0.35%/year degradation and the total absence of LID and LeTID, is the most robust choice if your horizon exceeds 25 years. REC guarantees 92% of output at 25 years.
To avoid: polycrystalline PERC.
To require:
• Product warranty ≥ 12 years (LONGi: 12–15 years, REC: 20–25 years, Aiko: 12 years).
• Performance warranty ≥ 25 years (90–92% at 25 years for HJT, 87–89% for TOPCon).
Frequently asked questions
Can a solar panel drop to 0% output?
Is degradation linear, or does it accelerate towards the end?
Can a panel degraded to 80% still be profitable?
How can I tell whether my panels are degrading abnormally?
Should you choose TOPCon or HJT in 2026?
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