How long solar panels last and how they age

A solar system is a long-term purchase. Most payback periods in Canada run well over a decade, so how long the equipment lasts matters as much as what it costs. The good news is that panels are among the most durable things you can put on a house. The parts that wear out sooner, mainly inverters, are predictable and can be budgeted for.

How long panels actually last

Solar panels have no moving parts. They are sealed layers of glass, silicon cells, plastic and an aluminium frame. Most failures come from manufacturing defects that show up early, or from physical damage such as severe hail.

The US Department of Energy cites a Berkeley Lab survey finding that the expected operating life of a solar panel has grown from around 20 years in 2007 to 25 to 35 years today. Many panels keep working well beyond their warranty, just at a somewhat lower output.

Two different panel warranties

Panel warranties come in two parts, and quotes don't always make the difference clear.

A common performance guarantee is that panels will still produce about 80% to 84% of their original rated power after 25 years. Some premium panels guarantee closer to 88% to 92%.

Read the fine print. A warranty is only as good as the company behind it. Ask who pays for labour to remove and replace a failed panel, since many product warranties cover the panel but not the cost of the crew. Your installer's workmanship warranty is a separate document again. Our guide on solar warranties explained goes deeper.

How fast panels lose output

All panels slowly lose output over time. This is called degradation.

A widely cited review by the US National Renewable Energy Laboratory looked at nearly 2,000 degradation rates measured in the field over 40 years and found a median of about 0.5% per year. Newer panel designs often degrade at a similar or slower rate. Many warranties allow a slightly larger drop in the first year, then a small steady decline after that.

At 0.5% per year, a panel would still produce roughly 88% of its original output after 25 years. Here is what that looks like for our Toronto sample system, which makes about 7,900 kWh in its first year:

SolarMyBill's savings estimates include panel degradation, so the long-term numbers you see already account for it. See our methodology.

Inverters wear out sooner

The inverter converts the panels' DC power into AC power for your home. It does constant electrical work, has electronic parts that age with heat, and is the component most likely to need replacing during a system's life.

• String inverters (one box, usually mounted near your electrical panel or on an outside wall) typically come with a 10 to 12 year warranty. Some can be extended to 20 or 25 years for a fee.
• Microinverters (small units under each panel) and power optimizers often carry 25-year warranties.

If you have a string inverter, it is sensible to assume you will replace it once during the life of the system and to set aside money for it. When comparing quotes, a longer inverter warranty has real value. Our guide on microinverters vs string inverters compares the two.

Other parts that age

• Racking and roof attachments are aluminium and stainless steel and should outlast the panels if installed properly. Flashing and sealant around roof penetrations deserve a look whenever the roof is inspected.
• Wiring and connectors can be damaged by squirrels or loosened over time. An annual look at your monitoring app will usually catch a problem.
• Batteries, if you have one, have their own warranty, usually measured in years and in total energy cycled. They typically wear out well before the panels.

What happens at 25 years

Nothing dramatic. The system doesn't shut off when the warranty ends. You will most likely have a working system producing somewhat less than when it was new. At that point you can:

1. Keep using it. If output is still reasonable and nothing has failed, this is usually the best value.
2. Replace failed parts as needed. A single bad panel or an old inverter can often be swapped out, though matching old panel sizes can be tricky.
3. Repower. Replace the old panels with new, more efficient ones on the same racking or new racking. This often coincides with a roof replacement.

Plan the roof. Removing and reinstalling panels for a reroof costs money, so it is best to start with a roof that has most of its life left. See replacing your roof before solar.

Recycling

Panels are mostly glass and aluminium, which are recyclable. Panel recycling programs in Canada are still developing and vary by province. Ask your installer what they do with old panels, and check with your municipality.

Next step

See how your estimated savings hold up over 25 years: check your roof.

Common questions

How long do solar panels last in Canada?

Most panels are expected to last 25 to 35 years, and many keep working longer at reduced output. Cold weather doesn't shorten their life.

How much efficiency do solar panels lose each year?

A large review of field data found a median loss of about 0.5% per year. After 25 years, a typical panel still produces most of its original output.

When will I need to replace my solar inverter?

String inverters usually carry 10 to 12 year warranties and often need replacing once during a system's life. Microinverters commonly carry 25-year warranties.

What happens to solar panels after the warranty ends?

They keep producing power, just a bit less than when new. You can keep using them, replace failed parts, or upgrade to new panels.

Sources

• NREL: Photovoltaic Degradation Rates, An Analytical Review
• US Department of Energy: End-of-life management for solar photovoltaics
• Clean Energy Reviews: Solar panel warranty explained
• GreenLancer: Solar inverter warranty guide