Most solar panels in the UK should last 25 to 30 years or more. Energy Saving Trust says panels should last around 25 years or more, and its maintenance guide puts the full lifespan at about 30 years. Panels slowly make less power as they age, but they rarely stop working all at once.

The part that wears out first is usually the inverter, not the panels. Energy Saving Trust says inverters typically need replacing every 10 to 15 years. This guide explains the slow loss in output, what warranties cover and how to plan for the costs. For the wider picture, see our hub on solar panel maintenance and lifespan.

How long solar panels really last

Solar panels have no moving parts. Sunlight hits the cells, and the cells make electricity. Because nothing spins or grinds, wear is slow.

Home Energy Scotland says solar panels should last 30 years or more. Energy Saving Trust gives two figures on two pages. Its solar facts page says 25 years or more, and its cleaning guide says around 30 years. The honest answer is a range, not a promise.

Several things shape where you land in that range:

  • The quality of the panels and how well they were fitted.
  • Weather, such as heavy snow, hail and strong wind.
  • Shade, bird nests and moss that go unchecked.
  • How well the roof itself ages underneath.

Your installer matters more than most people expect, because roof fixings and wiring decide a lot. A neat install with sound roof fixings protects the panels for decades. Our guide to choosing a solar installer explains how to check credentials before you sign.

What degradation means

Degradation is the slow fall in output as panels age. A panel that made 400 watts in ideal light when new will make a little less each year. You will not notice it from one month to the next, since the fall is so small.

The National Renewable Energy Laboratory (NREL), a US government lab, gathered nearly 2,000 degradation rates from published studies. It found a median loss of 0.5 percent a year. That is a middle value, so some panels lose less and some lose more.

What 0.5 percent a year adds up to

Here is a simple worked example. At a loss of 0.5 percent a year, a panel would still give about 88 percent of its first-year output after 25 years. That is our own sum from the NREL median, and not a promise for your panels.

Your real figure depends on the brand, the climate and the install. So read the maker’s performance warranty rather than relying on a general figure. It states the output the maker will stand behind, and for how long.

Why output also changes for other reasons

Not every dip is degradation, because weather matters too. Output also changes with the weather, with the season and with shade. Our post on solar panels in winter shows why a December reading is far lower than a June one. A fair comparison looks at the same month across several years.

The inverter: the part to plan for

The inverter changes the direct current from your panels into the power your home uses. It works every daylight hour, so it wears faster than the panels. That is why it fails first. Energy Saving Trust says inverters typically need replacing every 10 to 15 years, and that this usually costs around £800.

That figure is a guide from one source, and your quote may differ. It is still helpful for planning. Energy Saving Trust puts a typical 4.5 kWp home system at around £7,600, so an £800 inverter swap is roughly a tenth of the original price.

Ask three questions before you buy. How long is the inverter warranty? Can it be extended? What would a swap cost, including labour? Our guide to solar inverters explained covers the types and what they mean for lifespan.

Warranties: what each one covers

A solar job comes with more than one warranty. Each covers something different, and the lengths vary, so compare them side by side. Get all of them in writing.

  • Product warranty. The maker promises the panel is free from defects. The length varies by brand.
  • Performance warranty. The maker promises a minimum output after a set number of years.
  • Workmanship guarantee. The installer promises the roof work and wiring are sound.

For homes, MCS says an insurance-backed guarantee is required. It must cover workmanship for at least two years. It must also pass to the next owner if you sell. If your installer stops trading, the insurer picks up the cover. That is why this guarantee matters.

Ask what the guarantee does not cover. Roof leaks caused by old tiles, for example, may fall outside it. Keep the MCS certificate, the handover pack and every warranty together, because a buyer will ask for them.

Looking after panels so they last

Light care protects the life of the system, because small faults grow if nobody spots them. Rain keeps most panels clean enough. A yearly look from the ground, plus a check of your monitoring app, catches most problems early.

The MCS installation standard (MIS 3002 issue 6.0) suggests an owner check each year, an installer visit about every 10 years and a full visit about every 15 years. These gaps are advisory, and your installer or insurer may ask for something different. Energy Saving Trust suggests a full professional service every three to five years, and says some installers need this to keep the warranty valid. Read your own warranty terms.

Our guide to cleaning and maintaining solar panels covers the safe way to do each job. Never climb onto the roof yourself, since roof work mixes falls with electric shock.

Does lifespan change the maths?

Yes, because the longer the panels last, the more years of savings you get. Home Energy Scotland gives a payback of around 8 to 12 years for a typical home. A panel life of 25 to 30 years leaves a good run of years after that.

However, do not stretch the sums too far. Allow for an inverter swap, and for a slow fall in output. Our post on whether solar panels are worth it walks through the full sum with these in mind.

A battery adds another part with its own life. However, it has its own warranty, so check the terms. Our guide to solar battery cost and sizing explains what to ask.

Selling a house with solar panels

Panels that are well kept help a sale. A buyer will want to see the paperwork, because it proves the system is legal and insured. That includes the MCS certificate, the guarantee, the inverter manual and your generation records.

Roof work is the other thing to plan around. For example, if you need to re-roof, the panels must come off and go back on, which costs money. Check the roof is sound before you fit panels, and ask about this at the quote stage. Panels on a house usually count as permitted development, but there are exceptions, as our post on whether solar panels need planning permission explains.

Cost also matters when you plan for the long term. VAT rules change the start-up price, so read our guide to 0% VAT on solar panels and batteries before you compare quotes. Our solar panel costs and savings hub puts these figures side by side. For the basics of how the parts fit together, see how solar panels work.

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Common questions

How long do solar panels last in the UK?

Energy Saving Trust says panels should last around 25 years or more, and its maintenance guide puts the full lifespan at around 30 years. Home Energy Scotland also says 30 years or more. Output slowly falls over that time.

How much output do solar panels lose each year?

A well-known US National Renewable Energy Laboratory review found a median loss of about 0.5 percent a year. Your own panels may differ, so check the maker's performance warranty.

Which part of a solar system fails first?

Usually the inverter. Energy Saving Trust says inverters typically need replacing every 10 to 15 years, at a cost of around £800.

Do solar panels still work after 25 years?

Yes, in most cases. They make less power than when new, but they keep working. Whether it still pays to keep them is a matter of your roof, your inverter and your bills.

What happens to the warranty if my installer closes?

An insurance-backed guarantee should cover you. MCS says homes must get one, and it must pass to the next owner if you sell. Keep the paperwork safe.