Commercial Solar Warranties: Product, Performance and Workmanship
Updated 23 October 2026 · SEO Dons Editorial
What layers of cover does a commercial system have?
There is no single warranty on a solar system. Each layer is a separate promise from a different party, with its own start date, conditions and remedy.
| Layer | Given by | What it addresses |
|---|---|---|
| Module product warranty | Module maker | Defects in the module itself |
| Module performance warranty | Module maker | Output falling below a stated level over time |
| Inverter warranty, with any extension | Inverter maker | Inverter faults for the stated term |
| Workmanship warranty | Installer | Faults in how the system was installed |
| Insurance-backed cover | Insurer, if bought | The workmanship cover if the installer stops trading |
| Roof warranty | Roofer or roof maker | Leaks and the effect of fixings, so keep it in the loop |
| Implied terms in law | Statute | Satisfactory quality and reasonable care and skill, which a contract can limit only within the law |
The installation guide shows when each document should reach you, and the guide to commissioning covers the handover pack.
How do module product and performance warranties differ?
The product warranty covers defects in the module. The performance warranty covers how much power it keeps producing. They have different lengths. REC's English-language warranty page, for example, lists a 20-year product warranty beside a 25-year power warranty. JinkoSolar's Tiger Neo page lists a 30-year linear power warranty. These are examples of the kind of figures involved, not a comparison, and terms vary by model and market.
Do not read a test standard as a warranty. IEC 61215-1 sets design qualification tests for modules suitable for long-term outdoor operation, and IEC says test results are not a quantitative prediction of lifetime. The warranty is the maker's own commercial promise. Degradation rates and how long panels last in practice are covered in the lifespan and degradation guide. What the product and performance warranty lines on a sheet mean in practice is explained under commercial PV panels.
REC's page also shows how labour cover can change with system size. It lists a 25-year labour warranty for systems up to 25 kW and a 10-year labour warranty for systems from 25 to 500 kW, paid as a set fee to a certified installer, and says the package is offered only through certified installers. Whatever the make, ask who pays for labour, access and replacement, and whether eligibility depends on who installed the system.
What does the inverter warranty add, and what conditions come with it?
MCS notes that solar panels themselves can last over 25 years, but the inverter may need replacing during that time. That makes the inverter terms worth more attention than their length suggests, and the repowering guide covers the replacement decision.
Fronius's UK warranty page shows how terms can change with size: its model for inverters under 50 kW states 10 years of cover once registered, and its model for inverters of 50 kW or more states 5 years. Cover depends on registering the inverter within 30 months of delivery and starts at commissioning. A paid extension can be bought only within 6 months of the start of the warranty period, and the page says that the manufacturer's system record, not the certificate, decides whether a warranty exists. It also says new inverters commissioned on or after 1 June 2026 must be registered on its portal.
Registration windows and deadlines can decide a claim, so put each one in the handover checklist, with the date it expires. The inverter types guide explains the architecture behind the choice.
What does a workmanship warranty cover, and what does the law add?
Installer workmanship cover is the layer buyers most often assume rather than read. For domestic customers, MCS requires installers to stand behind workmanship for at least two years, transferably, and to insure that promise against the installer ceasing to trade. That rule is written for domestic work, so a commercial buyer has to ask for the equivalent in the contract: length, transferability on sale of the building, and what is excluded.
The law sets a floor under any contract between businesses. The Supply of Goods and Services Act 1982 implies a term that goods transferred in the course of a business are of satisfactory quality, and, in section 13, that a supplier acting in the course of a business will carry out a service with reasonable care and skill. The Unfair Contract Terms Act 1977 says a term cannot exclude or restrict liability for negligence causing loss or damage other than death or personal injury except where it satisfies the requirement of reasonableness. A warranty therefore adds to those rights; it is worth checking that its wording does not claim to replace them.
Time limits matter on a long warranty. The Limitation Act 1980 sets six years for an action founded on simple contract and twelve for an action upon a specialty, counted from when the cause of action accrued. How those periods interact with a particular warranty, including any notice clause, is a question for a solicitor.
What is insurance-backed cover, and who gets it?
In MCS's description, an insurance-backed guarantee (IBG) is an insurance policy that backs the original guarantee given by a contractor, and it gives cover if the contractor ceases to trade during the guarantee's term. MCS's page on these products is framed around domestic installations, and says a policy is valid only once the premium has been paid and the physical policy has been issued, with a maximum period of cover of up to 10 years. For installations under its redeveloped scheme, MCS describes approved financial protection products giving at least six years of cover, framed around consumers buying for homes and small businesses.
A large commercial buyer should therefore not assume it is within any of those wordings. Ask in writing:
- who the insurer is and what the policy number is;
- that the premium has been paid and the policy issued, and to whom;
- whether the cover period matches the workmanship period;
- whether the policy pays out only on insolvency or also when the installer refuses to repair;
- whether a commercial customer of this size is within its terms, and what the excess is.
The separate question of insuring the installed system itself is covered in the commercial solar insurance guide.
How do you read the small print?
- Start date: delivery, commissioning or registration, and what must happen for cover to begin.
- Remedy and cost: repair, replace or pay, and who pays labour, access, removal and reinstallation.
- What counts as a defect: any carve-outs for soiling, shading, surges or unapproved repairs.
- How a performance claim is measured: the baseline, the test conditions, who measures and who pays for the test.
- Conditions: maintenance, cleaning, monitoring or firmware duties that keep cover alive.
- Transfer and notice: whether cover passes to a buyer of the building, and the deadline and form of a notice.
What is a sensible claims process?
- Record the fault: date, photographs, fault codes and monitoring screenshots.
- Work out which layer applies, using the table above, and find its notice clause.
- Notify in writing, quoting serial numbers, system address and the evidence.
- Keep an access log, and use only contractors the warranty allows to work on the equipment.
- If the installer does not respond or has stopped trading, go to the maker directly and to the insurer if a policy exists.
- Keep every reply with the handover file, because the next claim may be years away.
Before signing, the vetting checklist shows how to confirm who stands behind each layer, and the installation guide shows where the warranty documents fall in the programme.
Sources
- IEC: IEC 61215-1:2021, checked 22 October 2026.
- REC Group: Empowering warranty (a manufacturer page, used only for facts about its own terms), checked 22 October 2026.
- JinkoSolar: Tiger Neo (same use), checked 22 October 2026.
- Fronius: Warranty models, UK (same use), checked 22 October 2026.
- MCS: Solar Panels; Insurance Backed Guarantee Products; Financial Protection, checked 22 October 2026.
- legislation.gov.uk: Supply of Goods and Services Act 1982, section 4; section 13; Unfair Contract Terms Act 1977, section 2; Limitation Act 1980, section 5; section 8, checked 22 October 2026.
Common questions
Does a 25-year performance warranty mean the panels are covered for 25 years?
Only for what the document says. A performance warranty addresses output falling below a stated level, not every fault, and it depends on its conditions, remedy and who is still around to honour it. Read the start date, the measurement method and the remedy before relying on the headline number.
Who handles a claim if the installer has gone?
Module and inverter warranties normally sit with their makers, so those claims continue if the maker is still trading and you hold the documents and serial numbers. Workmanship cover is the layer that depends on the installer, which is why insurance-backed cover, where it exists, matters. Ask for the policy before signing.
Can an exclusion clause remove my legal rights?
Not entirely. The Unfair Contract Terms Act 1977 requires a term limiting liability for negligence to satisfy the requirement of reasonableness, and the implied terms in the Supply of Goods and Services Act 1982 apply to business contracts. A solicitor should read any clause that claims to replace them.
Should the warranty transfer if the building is sold?
It is worth asking for, particularly for workmanship cover and the inverter. MCS requires transferability for domestic workmanship warranties, so a commercial buyer should write the equivalent into the contract. Check how a new owner registers or notifies the change.