How long do solar panels last?

The Department of Energy reports an average operational lifespan of 25 to 35 years for panels in 2025, up from about 20 years in 2007. Panels keep producing past their warranty term, at slowly declining output.

How much do solar panels degrade per year?

A review of nearly 2,000 measured rates by researchers at NLR (formerly NREL) found a median of 0.5 percent per year. Your panel's performance warranty states the maximum loss the manufacturer allows.

How often does a solar inverter need to be replaced?

DOE says string inverters usually last 10 to 15 years. Microinverters tend to last about as long as the panels, though individual units can fail and are replaced one at a time.

Is a 20-year-old solar system worth repairing?

Often, yes. At the median degradation rate the panels still produce roughly 90 percent of their original output, and the usual failure point is the inverter or a connection. A service visit tells you which.

Panel lifespan

How Long Solar Panels Last and How Fast They Degrade

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Address: 2724 Dorr Ave, Suite 102, Fairfax, VA, 22031, US
Telephone: (571) 444-6886

The Department of Energy puts the average operational life of a solar panel at 25 to 35 years for panels in 2025. Output declines slowly: a national lab review of nearly 2,000 measured rates found a median loss of 0.5 percent per year. The inverter usually wears out before the panels.

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Reviewed 2026-09-24

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Answer first

How long solar panels last

Panels installed today are expected to run for decades, losing a small share of output each year. The parts that need attention sooner are the inverter, the roof under the array, and the connections. Plan the roof and the inverter around the panels, not the other way around.

Lifespan: DOE reports the average operational life grew from about 20 years in 2007 to 25 to 35 years in 2025.
Degradation: median 0.5 percent per year across nearly 2,000 measured rates (Jordan and Kurtz, NLR, formerly NREL).
Inverters: DOE says string inverters usually last 10 to 15 years; microinverters tend to last about as long as the panels.
Roof: Fairfax County advises a roof less than five years old before solar goes on.

What the lifespan numbers mean

A solar panel does not stop working at a set age. It produces a little less each year until the output, or a physical failure, makes replacement worth it. The Department of Energy's end-of-life page reports that the average operational lifespan of a panel rose from around 20 years in 2007 to 25 to 35 years in 2025, as materials and manufacturing improved.

Lab testing supports long life but does not predict it. IEC 61215, the design qualification standard for modules, runs panels through a sequence of environmental and mechanical stress tests. The IEC states plainly that those results are not a quantitative prediction of module lifetime, which depends on design, environment, and operating conditions.

How fast panels degrade

Degradation is the slow loss of output from sunlight, heat, and weather. The best-known review of field data, by Dirk Jordan and Sarah Kurtz at the national lab now called NLR (formerly NREL), assembled nearly 2,000 degradation rates measured on modules and whole systems over 40 years of field testing. The median was 0.5 percent per year.

At that median rate, a panel keeps roughly 90 percent of its original output after 20 years. Some panels do better and some worse, which is why the manufacturer's performance warranty matters: it is the written ceiling on how much output the panel may lose.

First year: performance warranties usually allow a larger loss in the first year than in each year after, so read the first-year figure and the yearly rate separately.
Heat: panels produce less on hot days than on cool, bright ones. Airflow under a rooftop array helps.
Damage: cracked cells, failed junction boxes, and water intrusion cause sudden drops, not slow ones. Those are warranty or repair items, not normal degradation.

Reading a panel warranty

Most panels carry two separate manufacturer warranties. Read both, and keep the paperwork with your home records.

Product warranty: covers defects in the panel itself. Check the term in years and whether it pays for labor to swap a panel or only the replacement panel.
Performance warranty: states the minimum share of rated output the panel keeps over its term. Read the first-year figure, the yearly decline, and the end-of-term percentage.
Claims: expect to need serial numbers, installation records, and monitoring data. A claim is much easier with a panel serial map made at installation.
Installer coverage: workmanship, roof penetrations, and wiring are separate from the manufacturer warranties. Ask each company what it covers and for how long.

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When to replace the inverter

The Department of Energy's consumer guide says string inverters usually last 10 to 15 years and may need replacement during the life of the panels, while microinverters tend to have lifetimes similar to the panels. On a string system, budget for one inverter replacement.

Replace an inverter when it fails, when it throws repeated faults the manufacturer cannot clear, or when it is out of warranty and a failure would leave the whole array offline for weeks. A replacement string inverter must be compatible with the existing strings and meet the current rapid shutdown rules, which can mean adding module-level devices on the roof at the same time.

Signs something is wrong

Normal degradation is too slow to notice month to month. A sudden change is the signal. DOE's consumer guide says a drop in energy production higher than 10 percent from year to year could indicate maintenance issues.

Monitoring shows zero production on a sunny day, or one panel reads zero while its neighbors produce.
The inverter shows a fault light or error code.
Your electric bill rises in spring and summer with no change in how you use power.
Water stains in the attic under the array, which point to an attachment, not the panels.

Plan the roof around the panels

The roof usually becomes the limit before the panels do. Fairfax County's Going Solar guidance says installations can last 20 to 25 years, so the roof should be less than five years old. If the roof needs replacement partway through, the array has to come off and go back on, and the attachments have to be reflashed.

When panels do reach the end of their service life, DOE's end-of-life program tracks recycling and reuse options as the number of retired panels grows. Most homeowners will face a removal for reroofing long before a replacement for worn-out panels.

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Who checks aging systems

AJ Long Electric is a licensed Virginia Class B contractor (license 2705031092) and has done electrical work in Northern Virginia since 1996. We service solar systems other companies installed, including orphaned systems whose installer has closed. Estimates are free.

Straight answers

Questions

How long do solar panels last?: The Department of Energy reports an average operational lifespan of 25 to 35 years for panels in 2025, up from about 20 years in 2007. Panels keep producing past their warranty term, at slowly declining output.
How much do solar panels degrade per year?: A review of nearly 2,000 measured rates by researchers at NLR (formerly NREL) found a median of 0.5 percent per year. Your panel's performance warranty states the maximum loss the manufacturer allows.
How often does a solar inverter need to be replaced?: DOE says string inverters usually last 10 to 15 years. Microinverters tend to last about as long as the panels, though individual units can fail and are replaced one at a time.
Is a 20-year-old solar system worth repairing?: Often, yes. At the median degradation rate the panels still produce roughly 90 percent of their original output, and the usual failure point is the inverter or a connection. A service visit tells you which.

Sources

Next step

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