Maintenance and fault-finding

Solar Panel Warranty UK: What's Covered and What Isn't

A solar panel warranty sounds straightforward until something goes wrong. A typical UK installation comes with three separate layers of warranty from two different parties, each covering different faults and each with its own exclusions. This guide explains what each layer covers, what can void it, and what to do when a panel or inverter fails.

Useful reference. This video is from a UK solar and renewables advice channel and covers the practical differences between product warranties, performance guarantees and workmanship cover for UK homeowners. "Solar Panel Warranties & Maintenance Explained | What UK Homeowners Need to Know" (August 2025).

1. Identify the three types of warranty

When you have solar panels installed in the UK, you receive three separate warranty documents from two different parties. The panel manufacturer issues two: a product warranty (covering manufacturing defects) and a performance guarantee (covering output degradation). The installing company issues one: a workmanship warranty covering faults caused by their installation work.

These are distinct. Losing the installer's details does not affect the manufacturer's warranty. Having the manufacturer go out of business does not affect the installer's workmanship cover. Understanding which document applies to which fault saves a lot of confusion when something goes wrong years down the line.

2. Check what the product warranty actually covers

The product warranty covers manufacturing defects in the physical panel: delamination of the encapsulant that holds the cells, junction box failures, internal cell cracking, frame corrosion, and electrical faults originating inside the panel. Most reputable panel brands offer 10 to 25 years on the product warranty; budget panels may carry only 5 to 10 years.

What the product warranty does not cover is equally important: physical damage from external causes (hail, falling objects, vandalism, lightning strike), installation damage, modifications made after fitting, and damage caused by using the panel in conditions outside its rated specification. External damage is covered by your home insurance, not the manufacturer. Read the exclusions section of the warranty document before the installation is complete so you know what you are and are not protected against.

3. Understand the performance guarantee separately

The performance guarantee runs alongside the product warranty but covers something different: it promises the panel will not degrade faster than a specified rate. A typical guarantee might read "at least 90 percent of rated output at year 10 and at least 80 percent at year 25 to 30". If your panels fall below those thresholds and you have monitoring data to demonstrate it, you have grounds for a claim.

Output below the guaranteed level must be sustained and documented: a poor output reading on a cold, cloudy March day is not a performance guarantee issue. You need monitoring data across multiple months showing consistent underperformance below the contracted threshold, corrected for temperature and irradiance. Your monitoring app exports this data; set up a baseline reading when the system is new so you have a reference point for comparison years later.

4. Check the workmanship warranty with your installer

The workmanship warranty comes from the company that installed your system and covers faults caused by how the installation was carried out: a roof penetration that leaks because it was not sealed correctly, cable management that fails because it was not UV-rated, a bracket that corrodes because the wrong fixings were used with a particular roof material, or a commissioning error that causes intermittent inverter trips.

Workmanship warranty lengths vary significantly: some installers offer two years, others ten. It is only as good as the company that backs it. If your installer goes out of business, the workmanship warranty becomes difficult to enforce, which is why trading history, company registration age, and MCS consumer code membership all matter when choosing an installer. Ask specifically about the workmanship warranty term before you sign anything.

5. Keep the documents that activate each warranty

Some panel manufacturers require the panels' serial numbers to be registered on their website within 90 days of installation for the full warranty term to apply. If the installer does not do this, you may default to a shorter standard term. At handover, ask your installer whether registration is required and whether they have done it. Ask for the confirmation email or registration reference.

Store the following in one place: the MCS certificate, each panel's product warranty and performance guarantee document, the inverter warranty confirmation, and the installer's workmanship warranty letter. If you sell the property, these documents pass to the buyer and are an important part of evidencing a compliant, warranted solar installation. Losing them does not make claims impossible, but it makes them harder.

6. Know what to do when something goes wrong

If output drops or a panel appears to have failed, start with your monitoring system. Most modern inverters log generation per string, and a battery or smart meter integration will show import/export changes. A single panel dropping to zero usually shows up as a string underperforming relative to its pair. Take screenshots and export the data before doing anything else.

Contact your installer. They are the right first point of contact regardless of whether the fault lies with their workmanship, the panel, or the inverter: they have the test equipment, know the installation, and can identify which warranty applies. If your installer is no longer trading, contact the panel manufacturer's UK distributor directly with the panel serial numbers. For inverter faults, contact the inverter manufacturer or their UK service agent.

Frequently Asked Questions

How long is the product warranty on UK solar panels?

Most solar panels sold in the UK come with a 10 to 25 year product warranty covering manufacturing defects. Budget panels from less-established manufacturers may carry only 5 to 10 years. The performance guarantee is separate and typically runs to 25 or 30 years, promising the panel will maintain at least 80 percent of rated output by year 25. The two documents are issued by the same manufacturer but cover different things: a panel can fail its product warranty without triggering a performance guarantee claim, and vice versa.

Does cleaning solar panels affect the warranty?

Cleaning itself does not void the warranty, but how you clean matters. Most manufacturers prohibit pressure washing, abrasive materials, and certain chemical cleaners. Using a pressure washer can damage the panel laminate and void the product warranty. The safest approach is deionised water with a soft brush or squeegee on an extension lance. If you are unsure, check the panel manufacturer's maintenance guide, which is usually available on their website. Some warranties require evidence of periodic maintenance to remain valid, so keeping a log of cleaning dates is good practice.

What happens to my warranty if the installer goes bust?

The panel manufacturer's product and performance warranty is independent of the installer: you claim directly from the manufacturer or their UK distributor. The inverter manufacturer's warranty works the same way. Only the workmanship warranty, which covers installation faults, becomes unenforceable if the company dissolves. This is one reason to choose an established installer with a trading history, and to check they are MCS-registered at the time of installation. The MCS Consumer Code provides a complaints route in some circumstances. Home insurance may cover consequential damage from a failed installation even if the installer is gone.

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