How long do solar panels last?

The panels: 25–30+ years

Most panels sold in the UK carry a 25-year performance warranty — a guarantee that output won’t fall below a stated level (typically 85–90% of original) within that period — on top of a 10–15 year product warranty against defects. Panels degrade slowly and predictably, at roughly 0.5% per year (estimate), so a panel making 430W today makes around 380W at year 25. There’s no cliff edge: plenty of 1990s arrays are still generating, just at reduced output. In practice, panels are usually replaced because a re-roof or an upgrade makes it convenient, not because they’ve stopped working.

The inverter: the wear item

The inverter is the hardest-working component and the one with a finite life: expect 10–15 years from a string inverter, with a replacement costing an estimated £800–£1,500 fitted. Microinverters (one per panel) often carry 20–25 year warranties but cost more upfront. Budgeting one inverter swap into your payback calculation is the honest way to model a 25-year system.

Batteries: cycles, not years

Home batteries wear by cycles — one full charge and discharge. Modern lithium iron phosphate units are typically warranted for 10 years or around 4,000–6,000 cycles (estimate), usually guaranteeing ~70% capacity remaining at the end. Used once daily, that’s a decade-plus of service; capacity fades gradually rather than failing, so an ageing battery still works — it just stores less. Size realistically with the battery calculator rather than oversizing to “future-proof”.

Mounting, cabling and the roof

Aluminium mounting rails and stainless fixings are effectively life-of-roof components. The roof itself is the real consideration: if your roof covering has under 10–15 years of life left, re-roof before installing — removing and refitting panels later adds scaffolding and labour costs that dwarf any saving from sequencing them together. A decent installer will tell you this at survey; it’s a good test of whether they’re decent.

Keeping output up

UK rain handles most cleaning on pitched roofs. What’s worth doing: glance at your monitoring app a few times a year (a sudden drop flags a fault while warranties are live), keep an eye on shading from growing trees, and service nothing — there are no moving parts to service. The lifespan story in one line: buy panels expecting 25+ years, an inverter expecting one swap, and a battery expecting a decade, and the system on your roof will very likely outlast the mortgage maths you bought it with.