Solar PV Warranties: Product, Performance, Workmanship and What O&M Actually Covers

Ask what warranty comes with a turnkey solar installation and you will usually be told twenty five years. It is a reassuring number, and it describes only one of at least four separate warranties in the package, each issued by a different party, each covering different things, and each failing in a different way.

The gaps between them are where problems live. A system can have a valid twenty five year warranty on paper and still leave you paying to fix it, because the thing that broke was covered by a different document, or because the warranty covers the part but not the labour to replace it, or because the company that issued it no longer exists.

This article separates the layers, explains where operations and maintenance begins and warranty ends, and sets out what to establish before signing rather than at the moment you need to claim.

The Four Layers

The module product warranty covers the panels themselves against manufacturing defects: delamination, junction box failure, frame corrosion, cell cracking that is not caused by handling. It is issued by the module manufacturer, not by your installer. Terms of ten to fifteen years are common, and premium manufacturers extend further. This is a defects warranty in the ordinary sense: the product was faulty, so the manufacturer replaces it.

The module performance warranty is the twenty five year figure people usually mean. It does not promise the panel will work; it promises the panel will still produce at least a stated percentage of its rated output at stated years. A typical curve allows a larger drop in year one and then a slow annual decline thereafter. It is a promise about degradation, and it only pays out when output falls below the guaranteed line, which is a much harder threshold to cross than most buyers assume.

The inverter warranty is separate again, issued by the inverter manufacturer, and typically far shorter: five to ten years, sometimes extendable at cost. This matters more than its length suggests, because the inverter is the component most likely to fail within the system's life. A twenty five year array paired with a five year inverter warranty means planning for at least one inverter replacement, probably two, and the budget for that belongs in the original business case rather than in a future surprise.

The workmanship or installation warranty is issued by the EPC contractor and covers their work: mounting, penetrations, cabling, terminations, labour and commissioning. Terms range from one to ten years and the variation is enormous. This is the warranty that covers the most common real-world failures, because most early problems are installation problems rather than product problems, and it is the one buyers scrutinise least.

Four warranties, four issuers, four different failure modes. The gaps between them are where problems live. Source: MIMAH engineering practice.

What a Performance Warranty Actually Promises

The performance warranty deserves a closer look, because it is the one most often misunderstood.

It guarantees a degradation trajectory. The manufacturer states that output will not fall below a defined percentage of nameplate at defined years, usually with a steeper allowance in the first year and a linear decline afterwards. Modern warranties commonly guarantee something in the region of 80 to 90 percent of original output at year twenty five, with the exact figure varying by manufacturer and product tier.

Three things limit what that promise is worth in practice.

The claim threshold is low. Output has to fall below the guaranteed line, not below what you expected. A system quietly producing 5 percent under its yield model, which is a meaningful revenue loss, is nowhere near a warranty claim.

Measurement is your burden. To claim, you must demonstrate that the modules are underperforming, corrected for irradiance, temperature, soiling and shading. That requires monitoring data of a quality most small systems never collect, and it means the claim rests on evidence you either gathered or did not. The technical fundamentals of module performance and degradation are well documented, but the measurement obligation still sits with the owner.

The remedy is usually modules, not money. Manufacturers typically settle by supplying replacement panels or additional panels to make up the shortfall. Shipping, labour, scaffolding, crane hire and the lost production while the work happens are often excluded. A warranty that supplies a free panel and leaves you a bill for installing it is still worth having, but it is not the thing people picture.

Underlying all of this is whether the modules were qualified to the recognised design and safety standards in the first place. The IEC module qualification standards are the reference point, and a module without current certification against them is a warranty risk regardless of what the warranty document says.

Where O&M Begins

Warranty and O&M are complementary, and the boundary between them is the source of most disputes.

Warranty covers defects. Something was faulty or was installed wrongly, and the responsible party puts it right.

O&M covers everything else: cleaning, inspection, monitoring, testing, consumables, and the wear that is not a defect. Nothing on the warranty side triggers unless something has actually failed, and a system can lose a great deal of output without anything failing at all.

The practical division on a commercial installation looks like this. Soiling losses, vegetation management, connection tightening, thermal imaging, string testing, inverter filter and fan replacement, monitoring platform upkeep and annual electrical inspection are all O&M. A cracked module, a failed inverter board, a corroded frame and a leaking roof penetration are all warranty, provided they are reported correctly and the warranty conditions have been met.

That last condition is the trap. Most warranties require documented maintenance, and failure to maintain the system voids the very warranty you were relying on instead of maintaining it. Neglect and warranty do not coexist. Our O&M contract guide covers what a competent maintenance arrangement includes, and why solar systems fail early covers what happens when they do not.

Where warranty ends and O&M begins. Most warranties require documented maintenance, so neglect voids the very protection it was substituting for. Source: MIMAH engineering practice.

Making a Claim

Claims fail on process at least as often as on substance. Four things decide the outcome.

Evidence. Monitoring data showing the loss, corrected for conditions, with a baseline from commissioning to compare against. A system with no commissioning baseline has a much weaker claim, whatever the actual fault.

Notification within the stated period. Many warranties require notice within days or weeks of discovery. Reporting a fault months after your monitoring first showed it can void an otherwise sound claim.

Chain of documents. Purchase records, serial numbers, commissioning certificates and maintenance logs. Serial numbers matter more than people expect: a claim on modules whose serials cannot be tied to your purchase is a difficult claim.

The right counterparty. Module claims go to the module manufacturer, inverter claims to the inverter manufacturer, and installation claims to the EPC contractor. Sending everything to the installer is convenient and works only while the installer is willing to act as your agent, which is not a contractual obligation unless it was written down.

The costs that fall outside almost every claim are worth budgeting for in advance: labour, access equipment, freight, and the lost generation while the fault is unresolved.

What Makes a Warranty Worthless

The issuer disappears. A twenty five year warranty from a manufacturer that exits the market is a document, not a protection. Manufacturer longevity, financial standing and local presence matter more than an extra two years of stated term. The same question applies to your installer for the workmanship warranty, and it is the same due diligence set out in our guide to choosing an EPC contractor.

No local presence. A warranty honoured only at a factory on another continent, with freight at your expense, is technically valid and practically unusable.

Exclusions that cover the likely causes. Read what is excluded. Heat, dust, humidity, salt, sand abrasion and grid instability are the conditions many of our sites actually operate in, and a warranty that excludes environmental damage in a dusty, hot climate has excluded the main failure mechanism.

Voiding conditions you cannot meet. Requirements to use approved cleaning methods, to maintain at defined intervals, to keep monitoring active, or to have work done only by certified technicians. All reasonable individually; collectively they are a set of conditions somebody has to actually track.

Transferability limits. If the building or business changes hands, does the warranty follow. On an asset with a twenty five year term, this is not a remote question.

Five things that make a valid warranty worthless in practice. All five are checkable before signing. Source: MIMAH engineering practice.

What to Establish Before Signing

Seven things, all of which are easier to get before the contract than after.

All four warranty documents in full, not a summary in the proposal. The proposal is marketing; the warranty is the contract.

The workmanship warranty term in writing, with what it covers and whether labour is included.

Whether labour, access and freight are covered under each warranty, or only parts.

The maintenance conditions required to keep each warranty valid, and who is responsible for meeting them.

The claim process and counterparty for each layer, with contact routes that do not depend on the installer's goodwill.

Inverter replacement budget and timing, treated as a planned cost rather than a failure.

A commissioning baseline, because every future performance claim is a comparison against it.

If the system is being delivered under a power purchase agreement rather than bought, the warranty position changes: the developer owns the asset and carries these obligations, and your protection is the performance guarantee in the PPA instead. That shifts the questions, and our guide to solar PPAs covers what to check there.

MIMAH's renewable energy team reviews warranty and O&M packages as part of turnkey delivery, and audits them on systems installed by others. If you have a proposal in front of you and want to know what the warranty actually covers before you sign, get in touch.