In short
Solar panels usually last 25 years or more, making a little less each year, but the inverter typically needs replacing at least once, after about 10 to 15 years. How long yours last depends on how well the system was fitted and looked after, from the connectors and fixings to birds and cleaning.
Your panels went up ten or fifteen years ago, the app shows less than it used to, and you're wondering whether the whole system is near the end. Or you're buying a house with an older system on the roof and want to know how much life is left in it.
How long solar panels last in the UK
The Energy Saving Trust says "your solar panels should last 25 years or more" (Energy Saving Trust). Panels have no moving parts, and 25 years isn't a switch-off date. It's roughly where many panel output warranties end, and well-kept panels carry on generating after that.
They do make a little less each year. A US National Renewable Energy Laboratory review of nearly 2,000 measured degradation rates found "a median value of 0.5%/year" (NREL). As a rough guide, at that rate a system makes around a tenth less after 20 years than it did when new.
The inverter, the box that converts the panels' electricity for your home, is a different story. The Energy Saving Trust says "you need to replace this after around 12 years", and most inverters last somewhere between ten and fifteen.
Which? says you're likely to have to replace yours at least once over the panels' lifetime (Which?).
What changes how long solar panels last
The make and model of panel. Warranties vary by maker and model, so the datasheet is the document to check. LONGi's warranty for its Hi-MO X6 home panels gives 25 years on the product for some models and 15 for others, and guarantees output for 25 or 30 years, falling by no more than 0.4% a year after the first (LONGi warranty). JA Solar lists 0.4% annual degradation over 30 years for its JAM54D40 panel (JA Solar).
Tony Beckett, our director, puts panel product warranties at "20 to 25 years". Of JA Solar, he says: "They're the ones we use the most."
What to do: find the make and model on your MCS certificate and look up that panel's datasheet, as Which? suggests.
The inverter. It's the part most likely to fail: in a Which? survey of more than 2,000 owners, inverter problems were the most common fault, reported by 15%. Most inverters come with at least five years' warranty, which you can often extend, but the Energy Saving Trust warns that "a 15-year warranty costs almost as much as a replacement inverter".
What to do: note when yours was fitted and plan for a replacement from around ten years. Our servicing page covers inverter repairs and replacement.
Connections and cabling. Electrical Safety First says problems "can occur through bad installations, poor quality connections and cable damage through vermin and weathering, particularly if cables have not been secured correctly" (Electrical Safety First).
What to do: have the DC connectors and cable runs checked on every service.
Birds under the panels. Pigeons nesting underneath can peck at or dislodge the cabling, and nesting material packed against a live array is a fire risk.
What to do: look for droppings, twigs at the edges and birds coming and going. Our guide to stopping pigeons nesting under solar panels covers the fix and what the law allows.
How the panels are cleaned. We recommend one to two cleans a year, depending on the area and the panel warranty. In Tony's words, "it all depends on the warranty of the panels, what they dictate as well." We never use pressure washers or detergents on panels.
What to do: check what your panel maker's manual allows before anyone cleans them.
Loose fixings and missed inspections. Rails, clamps and roof anchors can work loose over the years, and a loose fixing is a safety problem before it's a performance one.
What to do: have the system inspected every one to two years, as the Energy Saving Trust recommends, with the MCS maintenance schedule as the minimum.
What we see on real jobs
The thing we see shortening systems most is neglect. Tony says a lot of the older systems we're called to haven't had a service in something like ten years, and bird proofing comes up on a lot of our jobs.
We also see owners worry about the wrong thing. A slow fall over many years is normal. A sudden drop usually points to the inverter, one string of panels or a connector, and some calls about a "dead" system turn out to be a monitoring or wi-fi problem, which we'd rather tell you than sell you a repair.
What an inverter replacement and a service cost
These are our published prices:
- A replacement inverter: £1,200 to £2,000 fitted. Tony's range is "depending on inverter", meaning its size and type. We keep some in stock and source others for the job.
- A routine service on a home system: around £200 to £300, with a written report afterwards.
- Bird proofing: around £400 to £800.
We repair where repair makes sense and replace where it doesn't, and we say which before any work starts. We also service systems we didn't install: our solar servicing and maintenance page lists what every service covers.
If you're on the Feed-in Tariff, a replacement doesn't have to cost you the tariff. Ofgem says you "may repair or replace all or some generating equipment without affecting the compliance of an accredited installation, provided that the installation continues to meet the scheme rules" (Ofgem FIT guidance).
When to call someone, and what to send
Call us if: generation has dropped sharply against the same month last year, the inverter shows an error or a red light, birds have got under the panels, or the system is ten years old or more with no service record. Check the monitoring is actually connected first. We're based in Warrington and work across the UK.
What to send us on WhatsApp:
- your postcode
- a photo of the panels, and one of the inverter including its label
- the MCS certificate, which names the make and model
- a few years of generation figures, or a screenshot from the monitoring app
- when the system was last serviced, if you know
That's how most of our jobs start. In Tony's words, "we do everything via WhatsApp".
Key points
Panels last 25 years or more. They don't stop at 25: well-kept panels carry on generating, a little less each year.
Expect a slow decline, not a cliff. The median loss in NREL's review is 0.5% a year, and your panel's datasheet gives its own figure. A sudden drop means something needs looking at.
Plan for one inverter. It usually needs replacing after 10 to 15 years, at £1,200 to £2,000 fitted.
Neglect is what shortens a system's life. Have the connectors, fixings and birds checked, avoid harsh cleaning, and book an inspection every one to two years.
Questions people also ask
What happens to solar panels after 25 years?
Nothing switches off at 25 years. Well-kept panels carry on generating, a little less each year, and you can keep running them while the output is worth having.
How much efficiency do solar panels lose each year?
A US National Renewable Energy Laboratory review of nearly 2,000 measurements found a median loss of 0.5% a year. Panel makers' own warranties are often tighter, for example LONGi guarantees no more than 0.4% a year after the first year on its Hi-MO X6 home panels.
How do I know if my solar inverter needs replacing?
The usual signs are an error code or red light, or generation well below the same month last year, especially on an inverter around ten years old. Check the monitoring is connected first, then have it looked at, because some faults can be repaired.
Is an extended inverter warranty worth paying for?
Compare its price with a replacement before you buy one. The Energy Saving Trust warns that a 15-year warranty costs almost as much as a replacement inverter, and a replacement from us typically costs £1,200 to £2,000 fitted.
Got an older system? Book a solar health check or send us a photo of your inverter on WhatsApp.
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