Product or Performance Warranty: What Is Actually Being Promised?

Published by Quinn Lai | By InverPower Technical Team

Published 22 August 2026 · Last updated 22 August 2026

Two numbers appear on every module brochure and clients read them as one long guarantee. They are not. One says the product will not be faulty; the other says it will not fade faster than a published curve. Quoting them as a single figure is where expectations get set wrong, and expectations set wrong at the sale are argued about at the claim.

The product warranty

This is the conventional one: if the item is defective in materials or workmanship within the stated period, the manufacturer repairs, replaces or credits it. On modules that period is typically a decade or more and has been lengthening; on inverters it is shorter and usually extendable at purchase; on batteries it is bounded by both time and throughput.

What matters more than the headline number is what the remedy actually is. Replacement with an equivalent product, a credit at a depreciated value, and repair are three different outcomes, and it is worth knowing which one applies before it is needed. Freight, labour, access equipment and the cost of removing and refitting are usually excluded, which on a rooftop array is most of the real cost of a claim.

The performance warranty

A different promise: that output will not fall below a stated share of nameplate at each year of the module's life. It is described by a first-year figure, an annual degradation rate thereafter, and an end-of-term figure — usually as a straight line, though stepped structures still exist. Modern n-type modules carry gentler curves than older p-type ones, which is a real commercial difference and not just a specification.

Claiming against it is harder than it sounds. The claimant has to demonstrate that a specific module's output is below the curve, which requires measurement under known conditions — flash test data or a supervised on-site measurement — rather than a monitoring screenshot. Soiling, shading and a fault elsewhere in the string all produce low readings that are not degradation, and the manufacturer will say so.

The other half of the promise is who is standing behind it. A twenty-five year guarantee is only as good as the manufacturer still being there in year twenty, and as good as their claims process being reachable from Malaysia. That is part of what bankability means when a lender's adviser asks about module selection, and it is a fair thing to raise with a client comparing an established brand against an unfamiliar one on price.

The two side by side

The four reasons claims fail

Rarely on the merits, and usually on one of four things. Installation outside the manufacturer's instructions — clamps in unapproved positions, mounting orientations the manual does not allow, torque values ignored. Modification, including drilling a frame or opening a junction box. Cleaning outside the approved method, which is why pressure washing appears in this article twice. And documentation: no serial numbers, no delivery note, no chain back to an authorised supplier.

The fourth is the one an EPCC can eliminate entirely at the point of purchase. Buying through an official distributor means the manufacturer can see where the goods came from, and the support route exists before it is needed rather than being negotiated during a dispute.

Quoting it to a client

Say both numbers and say what each one means, in one line each. Then say what the warranty does not include — freight, labour and access on a claim — because that is the sentence that prevents the argument later. A client who understands that a replacement module arrives free and does not fit itself is a client who will accept a service quotation without feeling misled.

For inverters, mention the extension option at the point of sale rather than in year nine, when it is usually no longer available. And where the client is comparing two proposals on price, the warranty terms are often the honest difference between them — worth putting side by side rather than leaving as a footnote.

Buying so the warranty holds

InverPower is an official distributor for the brands we carry, which means the goods arrive with documentation that ties serial numbers to the manufacturer and a support route that works when something goes wrong. Send the bill of materials and we will tell you what is in stock, what the warranty terms are for each item, and what the extension options look like where they exist.

Frequently Asked Questions

Does a warranty claim have to go through the original installer?

Not usually, but the claim does have to be supported by the original purchase documentation, which the installer normally holds. Where a client has changed contractor, the handover pack is what makes the claim possible — another reason for serial numbers and delivery notes to sit with the client rather than in a supplier's file.

What voids a performance warranty?

The same things that void the product warranty — installation outside the manufacturer's instructions, modification, misuse — plus cleaning methods the manufacturer does not approve. Damage from a pressure washer, abrasives or unapproved detergents is treated as misuse rather than degradation.

Do warranties cover the cost of replacing a failed module?

The module, usually. The labour, access equipment and freight to get it up onto the roof, usually not. That gap is worth stating in the proposal, because it is where clients feel misled if it appears for the first time during a claim.

Are longer warranties always better?

Only if the terms behind them are. A long headline period with a depreciated-credit remedy and a narrow claims window can be worth less than a shorter one with straightforward replacement. Read the remedy and the exclusions, not just the number of years.

Sources

• IEC — IEC 61215 series, Terrestrial photovoltaic modules: design qualification and type approval, including degradation testing — https://webstore.iec.ch
• IEC — IEC 61730-1 and IEC 61730-2, Photovoltaic module safety qualification — https://webstore.iec.ch
• Trinasolar — module product and performance warranty terms and degradation curves — https://www.trinasolar.com
• Sungrow — inverter and battery warranty terms, including extension options — https://www.sungrowpower.com
• IEC — IEC 62446-1, documentation requirements that support a warranty claim — https://webstore.iec.ch

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