How long do solar panels last?

Three parts, three very different answers.

The panels: 30 years and more

Panels have no moving parts, and they fail far less often than people expect. What they do is lose a little output every year.

• The warranty: current panels from the big makers come with a 30-year power warranty. LONGi’s Hi-MO 7, for example, guarantees no more than 0.4% loss a year, which leaves around 87% of the original output at year 30.
• Real-world loss: the US National Renewable Energy Laboratory looked at around 2,000 measured systems and found a median loss of 0.5% a year.
• The product warranty (cover against the panel itself being faulty) is shorter, typically around 12 years. Check the datasheet for the exact panel you are quoted.

What that means on a Hereford roof: a 4kW south-facing system makes around 3,990 units in its first year, going by the EU’s PVGIS solar data for the city. At 0.5% a year it is still making around 3,500 units in year 25.

Panels that stop working completely are almost always down to something else: water in a connector, a damaged cable, a bird problem. All of it is fixable.

The inverter: plan on replacing it once

The inverter turns what the panels make into power the house can use. It is the working part of the system, and it does not last as long as the panels.

The Energy Saving Trust’s guidance is 10 to 15 years. Over the life of a system, budget for one replacement.

This is the most common solar repair we get called to, by a distance. An inverter showing a fault code or a blank screen is usually a replacement, and it does not need the firm who fitted the original. Solar panel repairs in Hereford.

The battery: 10 to 12 years

Batteries wear with use, like the one in your phone.

• GivEnergy warrants its home batteries for 12 years, to keep at least 70% of their usable capacity.
• Tesla’s Powerwall warranty is 10 years, also to 70%.
• The Energy Saving Trust puts typical battery life at 10 to 12 years.

So a battery fitted with the panels will probably be replaced once while the panels carry on. That is worth knowing before you decide, and it is one of the things we cover in do you need a battery with solar?

What actually shortens a system’s life

• Shoddy connectors and cable runs. Mismatched or badly crimped connectors let water in. This is where most faults start.
• Outdoor isolators. Rotary isolators fitted outside are a known weak point once water finds its way in.
• Birds. Pigeons nest under arrays and chew the cable. Bird mesh fitted at install time stops it, which is why we fit it as standard.
• Nobody looking at it. A system quietly making less than it should costs you every month without announcing itself. Check your generation against the same month last year.

The short version

Panels: 30 years or more, losing about half a percent a year. Inverter: replace once, at 10 to 15 years. Battery: 10 to 12 years.

If you are thinking about solar, the survey is free. If you already have it and it is not doing what it should, send us a photo of the inverter screen.