How long do solar panels last?

The short answer: twenty-five to thirty years

Modern residential solar panels are designed, tested, and warrantied for a twenty-five to thirty year service life. Many continue producing useful power well past that, just at reduced output. The panels themselves are the most durable component of the system.

What wears out on a solar system

Panels

Panels are glass, silicon, aluminum, and wiring. They have no moving parts. They sit on your roof in the weather for decades. Quality panels degrade around half a percent per year on average, so after twenty-five years you are still producing roughly eighty-five to ninety percent of the original rated output.

Panels fail rarely, and when they do, it is usually a manufacturing defect in the first few years, covered by warranty.

Inverters

Inverters are the electronics that convert direct current from the panels to alternating current your home uses. They are the shortest-lived component of a solar system. There are two main types:

• String inverters live in a utility box at ground level and typically have a fifteen-to-twenty-year life. Many homeowners with string inverters replace them once during the panel warranty period.
• Microinverters are installed at each panel and are warrantied for twenty-five years, matching the panels. They typically last the full life of the system without replacement.

On shaded roofs (common in Richmond, parts of Montgomery County, and older Baltimore neighborhoods), microinverters are almost always the right call, both for production and for longevity.

Racking and mounting hardware

Aluminum or stainless racking is engineered to match or exceed the roof life. Under normal conditions it does not fail within the panel warranty period.

Wiring and conduit

Standard electrical components with decades of service life under normal conditions.

The degradation curve

A quality panel loses around one to two percent in its first year, then approximately half a percent per year after that. So:

• Year 1: roughly 98 to 99 percent of rated output
• Year 10: roughly 93 to 95 percent
• Year 25: roughly 85 to 90 percent

Honest production estimates bake this curve in. If a proposal shows level production year over year, it is ignoring reality.

Warranty coverage

• Product warranty (typically 25 years): covers manufacturing defects in the panel itself.
• Performance warranty (typically 25 years): guarantees a minimum percentage of original output at defined milestones.
• Inverter warranty: 15 to 25 years depending on type.
• Workmanship warranty from the installer: covers the installation itself, including roof penetrations.
• Production guarantee from the system owner on a Solar Lease or PPA: if the system underproduces against modeled output, you are made whole. This is separate from, and in addition to, the manufacturer warranties.

What happens after year twenty-five?

A few paths:

• Keep running. Most systems keep producing past warranty. You are not obligated to replace anything on a schedule. If production is still worthwhile, use the system.
• Replace panels. Technology improves. Newer panels at year twenty-five will be cheaper and more efficient than what is on the roof now. Replacing them gives you another twenty-five years at higher output.
• Decommission. If the system no longer makes sense, remove the panels. Roof penetrations are patched.

On a leased or PPA system, end-of-term options are in your contract. Typical choices: buy the system out at its then-value, renew the agreement at a revised rate, or have it removed at no cost to you.