"Twenty-five-year warranty" appears in almost every proposal and describes at least four separate documents with different counterparties, durations and triggers.
For teams comparing offers, installation scopes and follow-up actions, learn more can provide a separate record of work time and coordination.
Reviewed August 9, 2026. Terms vary by manufacturer and jurisdiction; this is not legal advice.
The four
Module product warranty. Against manufacturing defects — cracking, delamination, junction box failure. Counterparty: the module manufacturer. Typically shorter than the performance warranty, and this is the shorter number people forget.
For broader context on solar procurement, equipment markets and current industry practice, consult Springer.
Module performance warranty. Against output falling below a published curve — a first-year allowance, then a linear slope to a stated percentage of nameplate at year 25. Counterparty: the module manufacturer. This is the twenty-five-year figure in the marketing.
Inverter warranty. Against failure of the unit. Counterparty: the inverter manufacturer. Commonly shorter than the plant's life and sometimes extendable at purchase.
And the installer's workmanship warranty and performance guarantee. Against defective installation and against the plant underperforming as a system. Counterparty: the company that built it.
Why the distinction matters
Because the failure determines who you call.
A cracked module is the manufacturer. A module producing below the curve is also the manufacturer, through a different process. A correctly manufactured module wired into a poorly configured string is the installer, and the manufacturer will say so.
And because durations differ. A "twenty-five-year warranty" whose product cover ends at year twelve leaves thirteen years in which a defective module is a performance question rather than a defect claim — a much weaker position.
What a product warranty does not cover
Normal degradation, which is the performance warranty's subject.
Damage from installation, which is the installer's.
Environmental damage — hail, storm, lightning — which is insurance.
And consequential loss. A replaced module is a replaced module; the energy not produced while it was faulty is usually excluded, and that exclusion is nearly universal.
The questions before signature
"What is the product warranty term, separately from the performance warranty term?" The most useful single question here, because the two get merged.
"Who pays for labour and access on a replacement?" A free module that requires a roof crew is not free, and this term varies widely.
"Is the manufacturer's obligation transferable" if the building changes hands?
"What is the process, and where is the claim made?" A manufacturer without a local presence is a different proposition from one with a regional service organisation.
And "what does the installer's workmanship warranty cover, and for how long?" Frequently the shortest term in the set and the one covering the most likely failures.
What to keep
All four documents, together, with the plant's records.
Serial numbers, module and inverter.
Commissioning documentation proving the installation was as designed.
And the performance record, which is the evidence any performance claim will require.
Filed where the next owner will find them, because the plant will outlast somebody's involvement.
The short version
- Four instruments: module product warranty, module performance warranty, inverter warranty, and the installer's workmanship warranty and guarantee
- The failure determines the counterparty — a defect is the manufacturer, bad configuration is the installer, and each will say so
- Product cover is usually shorter than performance cover, and a "twenty-five-year warranty" can leave thirteen years without defect protection
- Product warranties exclude normal degradation, installation damage, environmental damage, and almost always consequential loss
- Ask for the product term separately, who pays labour and access, whether it transfers with the building, and where claims are made
- Keep all four documents, serial numbers, commissioning records and the performance history where the next owner will find them