How Long Do Solar Panels Last? Degradation in Plain Numbers

A customer once asked us, “If the warranty is 25 years, does the panel stop working on day one of year 26?” Fair question. The answer is no. Panels keep producing for a long time. They just produce a bit less every year.

What degradation means

Degradation is the slow loss of a panel’s power over time. Sunlight, heat cycles and moisture gradually wear the cells and materials. It’s normal and expected.

Typical numbers from current datasheets:

• First year: around 1 to 2% drop (smaller for N-type panels)
• After that: around 0.4 to 0.55% per year

What that looks like over time

Take a 580W panel with 1% first-year loss and 0.4% a year after:

So after 30 years, that panel still gives most of its original power. For a household, the change is gradual enough that you might not notice it year to year.

What makes panels age faster

• Micro-cracks from rough handling, people walking on panels, or hail.
• Hot spots from long-term partial shading or bird droppings left for months.
• Poor quality backsheets and encapsulants on cheap, untraceable panels.
• Water ingress at the junction box if seals fail.

Product warranty vs performance warranty

Panels usually have two warranties. The product warranty (often 12 to 15 years) covers manufacturing defects. The performance warranty (25 to 30 years) promises a minimum power output over time. Keep your purchase invoice and the panel serial numbers safe, you’ll need them for any claim.

What about the inverter and battery?

Panels usually outlive everything else in the system. An inverter is commonly expected to last around 10 years or more with good ventilation and protection, and batteries depend on cycles and heat. Planning for an inverter replacement somewhere in a panel’s life is sensible.

For more on panel types and ageing, read Mono PERC vs N-type TOPCon.