- What a solar panel warranty covers
- What a solar panel warranty does not prove
- How to read a solar panel warranty before you buy
- Frequently asked questions
- Is a 25-year solar panel warranty a 25-year life?
- Does the solar panel warranty include the inverter?
- Will a dirty array qualify under the performance warranty?
- Sources and references
A solar panel warranty is a contract about two different failures. One is a defect in materials or workmanship. The other is power falling below a stated share of the nameplate. They are not the same promise, they are not the same number of years on every module, and a warranty is not a measurement of how long the module will last. Pacific Northwest National Laboratory, describing field practice, says panel warranties are often 10 years and sometimes 25, while inverter warranties are typically 5 years with extensions to 10 or 15. That is what that operations page calls typical. It is not a law, and it is not your PDF.
A specification can demand more than the market’s average contract. The National Laboratory of the Rockies Standard Work Specifications, in the 2025 redline of section 11365, require a product and workmanship warranty of at least 10 years and a performance warranty of at least 80 percent of nameplate for at least 25 years. Inverters under that specification are at least 10 years, and the installer warrants the whole system for at least a year. Those are requirements for work that follows the specification. They do not rewrite a contract that says something shorter.
What a solar panel warranty covers
Read the two clocks separately. The product warranty is about a module that fails because it was built wrong: a bad junction box, a delamination, a cracked frame from a defect rather than from someone walking on it. The performance warranty is about watts. It usually allows a drop in the first year and then a smaller drop each year after, and it pays, if it pays, when measured power is below the promised floor. Xcel Energy’s 2023 module guidelines, which are one utility’s procurement rules, ask for at least 10 years of product coverage and at least 25 years of power coverage, with degradation after year one no more than 0.5 percent per year. They also ask that a bifacial warranty cover the rear as well as the front, and that a serial-defect clause exist. That is a buyer’s spec. A module that was not sold into that program does not inherit it.
Labor is often outside both clocks. A 25-year power warranty that ships a replacement module and leaves the crane, the roof, and the electrician to you is a different promise from one that includes removal and reinstall. The SWS installer warranty of at least one year is about the installation, not about the manufacturer coming back in year twenty. Ask who pays for access. On a roof, access is the expensive part. PNNL ties maintenance cost to how hard the array is to reach.
Damage you cause is outside. Walking on glass, a pressure washer, a strike that the warranty excludes, and a system voltage above the module’s maximum are not workmanship claims. Soiling is not a defect. A low-tilt array in a dry climate can lose output to dust that a wash would remove. That loss is operations, described in how to clean solar panels, not a warranty event.
What a solar panel warranty does not prove
It does not prove the module will still be at 80 percent in year 25. It proves that if a test, done the way the contract requires, shows it is below the floor, a remedy exists. The test is not a glance at the monitoring portal. Portals estimate. A warranty claim wants a measurement procedure, often at standard test conditions or a translation to them. Xcel’s 2023 module requirements say the datasheet has to state nominal power under standard test conditions, and that factory flash tests are run at those conditions under IEC 61215-2. A hot roof will read lower on a sunny afternoon without any defect at all. The datasheet’s temperature coefficients are the rate, and that same Xcel document requires them to be printed. How heat moves output is in how heat affects a solar module.
It does not transfer automatically when the house is sold, unless the contract says it does and the new owner registers in time. It does not cover the inverter unless the inverter has its own warranty. PNNL’s typical inverter term, about 5 years before an extension, is shorter than the module performance term in the SWS. Budget the inverter as the part that may be replaced while the modules are still under a power warranty. That is a planning split, not a prediction that your inverter fails in year five. A small set of inverters in a Sandia field check showed no appreciable degradation over the years of that particular check. One fleet is not a category lifetime.
A performance warranty also does not absorb shade, snow, or a failed string. Those cut output and they are not degradation of the cells. Snow losses modeled for fixed-tilt arrays in the continental United States ran from about 0 to 16 percent of annual energy, with some Alaska sites higher. That is weather, discussed in snow on solar panels. Do not file it as a defect.
How to read a solar panel warranty before you buy
| Line in the solar panel warranty | What to ask |
|---|---|
| Product or workmanship years | Is it the SWS-style 10-year floor, shorter, or longer? Defects only, or also labor? |
| Performance floor and year | 80 percent at 25 years is a program requirement, not a universal clause. What does this PDF say, and is year-one drop separate? |
| Bifacial rear side | If the module is bifacial, does the power warranty include the rear, as Xcel’s buying rules require for that utility? |
| Who pays the crane | Module-only replacement leaves roof labor with you. Get that sentence in writing. |
Keep the serial numbers and the flash-test data that came with the pallet. A claim without them is a conversation. Registration windows are in the contract. Miss them and the years you paid for may not start.
Frequently asked questions
Is a 25-year solar panel warranty a 25-year life?
No. It is a remedy if power falls below the contract floor and you claim it correctly. PNNL’s field note that some panel warranties are 25 years is about the paper, not a measured survival curve. Modules can outlast the paper or fail inside it.
Does the solar panel warranty include the inverter?
Not unless the inverter warranty says so. Typical inverter terms in PNNL’s operations guide are shorter than a 25-year module performance term. Under the SWS, the inverter floor is 10 years and the module performance floor is 25. Your contract can differ from both.
Will a dirty array qualify under the performance warranty?
No. Soiling is reversible with the right wash and it is not a materials defect. Measure after the glass is clean, under a method the contract accepts. A hot afternoon reading is not that test.
Sources and references
Typical warranty lengths as field practice, not a statute: Pacific Northwest National Laboratory. Program minimums of 10 years product, 80 percent for 25 years, 10-year inverter, 1-year installer: NLR Standard Work Specifications, 11365 history. One utility’s buying rules, including 0.5 percent per year after year one and rear-side coverage for bifacial: Xcel Energy PV module technical requirements, November 2023. Snow-loss range, which is not degradation: NREL snow model.
