The three warranties you should have
Panel product warranty covers manufacturing defects in the physical panel — delamination, frame corrosion, junction box failure, cell cracking that is not physically caused. Standard duration is 10–12 years; premium brands offer 25 years. This warranty is with the panel manufacturer, not your installer.
Panel performance warranty guarantees a minimum power output over time — typically 80% of rated output at 25 years. If your panels degrade faster than the warranted rate, the manufacturer should replace or compensate. This is separate from the product warranty and typically runs 25 years from installation.
Workmanship warranty covers the installation itself — cable routing, mounting hardware, waterproofing penetrations, and the quality of electrical connections. This is with your installer and typically runs 2–10 years depending on the company. Installers registered with the Solar Trade Association (STA) are required to offer a minimum 2-year workmanship warranty.
Inverter warranty is separate and varies by brand: Fronius offers 5 years standard (extendable to 20); SMA 5 years (extendable to 10); SolarEdge 12 years standard on HD-Wave; Enphase microinverters 25 years. The inverter warranty is with the inverter manufacturer.
Step 1 — Identify which warranty applies
Most problems fall into one of three categories. If a panel is physically cracked, delaminating, or corroded in a way not caused by external impact, this is a manufacturing defect covered by the panel product warranty. Contact the panel manufacturer directly using the model number and serial number from the panel label (visible from the ground if the label is on the front, or from the roof or your installation documents).
If the inverter is displaying a persistent fault code or has failed completely, this is an inverter warranty claim. Contact the inverter manufacturer or their UK service partner with the inverter serial number.
If the mounting system has failed, a roof penetration has started leaking, or wiring has been inadequately routed, this is a workmanship claim against your installer. If your installer has gone out of business, check whether they were part of any installer guarantee scheme — the STA and some local authority schemes offered third-party workmanship guarantees.
Documenting the problem
Before making a warranty claim, document the issue clearly. Take photographs of any visible damage from the roof (if you can do this safely) or from the ground. Download and save at least 90 days of monitoring data from your inverter portal showing the underperformance.
If the problem is degradation-related, you will need evidence that degradation exceeds the warranted rate. This means a formal power output measurement at standard test conditions (STC) — 1,000W/m² irradiance, 25°C cell temperature — carried out by a qualified technician with calibrated equipment. Panel manufacturers typically require this measurement before processing a degradation claim.
Keep all installation documentation: your MCS installation certificate, panel model and serial numbers, inverter serial number, and the original invoice. Without these, warranty claims become significantly harder to process.
What to expect from the claims process
Panel manufacturer warranty claims for manufacturing defects are usually processed by a UK distributor or service agent acting on behalf of the manufacturer. Response times vary — a simple product warranty claim on a physically failed panel from a well-established manufacturer is typically resolved in four to eight weeks. Complex degradation claims requiring on-site measurement can take longer.
If the manufacturer disputes your claim or has become insolvent, your consumer rights under the Consumer Rights Act 2015 may provide additional protection if the goods were not of satisfactory quality at the time of sale. This applies to your installer, who sold you the panels — not to the manufacturer directly, unless you purchased the panels separately.
For workmanship claims where the installer has ceased trading, check whether you paid by credit card. Section 75 of the Consumer Credit Act makes the card provider jointly liable for breaches of contract where the cash price of the goods or services was over £100 and under £30,000.