Guide
How long do solar panels last, and what fails first?
Panels degrade slowly and outlive their warranties. The inverter is usually the first real cost, and the roof underneath is the one people forget.
Updated September 18, 20262 min readAwaiting expert review
Written from primary sources by our editorial team. A credentialed reviewer hasn't signed off yet, so this page isn't in search results. It's information, not professional advice.
Not sure where to start? Take the Solar Check.About 2 minutes. Rough answers are fine.Panels do not usually fail; they fade. That distinction is the key to understanding what a solar system actually costs over its life, and where the real replacement cost sits.
Degradation, not failure
Output declines slowly and predictably. That is why production models project decades ahead with reasonable confidence, and why NREL's PVWatts is useful as a planning tool rather than a guess. Cumulative degradation is worth including in any long-run calculation, and it is one of the things a simple payback figure leaves out.
The inverter
The component that converts DC from the panels into AC for the house. A central string inverter commonly needs replacing somewhere around year 12 to 15. Microinverters and power optimisers sit under individual panels and carry their own warranty terms, often longer, with the trade-off that replacing one means going onto the roof.
Ask what type your proposal uses, what its warranty term is, and what a replacement is likely to cost. Very few proposals volunteer this.
Warranties and the company behind them
Most panel warranties promise a stated share of original output at year 25. That is meaningful only if the manufacturer still exists to honour it. The same applies to the installer's workmanship warranty — and in this industry, installers closing is common enough that it is a reasonable question to ask about before signing.
Bottom line
Assume decades of gradually declining output, one inverter replacement, and a roof that has to outlast the array. Then the economics in are solar panels worth it now and the price in what solar costs to install are the rest of the picture.
Common questions
How long do panels actually last?
They degrade rather than fail — typically around half a percent of output a year — so a panel is usually still producing most of its rated output after twenty-five years.
What fails first?
The inverter, commonly somewhere around year 12 to 15 for a string inverter. Microinverters and optimisers have their own warranty terms.
Does a 25-year warranty mean 25 years of life?
It means the manufacturer will stand behind stated output for that period, if the manufacturer still exists. That last clause is not a small consideration in this industry.
What about the roof?
The roof under the array is the thing people forget. If it needs replacing during the system's life, the array has to come off and go back on.
Sources
- U.S. Department of Energy: Homeowner's guide to going solar
- NREL: PVWatts Calculator
- NREL: Solar market research and analysis
- NREL Developer Network: PVWatts v8 API documentation
By SolarRealCost Editorial Team. First published September 18, 2026. Advertiser disclosure
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