Solar PV panels can expect to have a working lifespan of 40 to 50 years. Solar panel degradation does occur and is 0.5% yearly on average for newer technology panels. This means that after 25 years, the solar PV panels will be producing 87.5% as much electricity as they did when they were first installed. The output warranty is at 80% productions at 25 years for most brands.
Real-life tests in Switzerland showed positive results. The LEE-TISO testing centre for photovoltaic components installed Europe’s first grid-connected PV plant back in 1982. They had the opportunity to inspect it 20 years later in 2002. The results showed an decrease of around 11% (only 0.5% per year) against the initial output rate.