Solar Panel Repairs UK: What Breaks, Who Fixes It, and What's Covered

Most UK solar panel systems run for years without needing any attention beyond an occasional clean. But every system has components with a finite lifespan, and when something does go wrong it helps to know exactly what has failed, who is responsible for fixing it, and what your warranties cover. This guide walks through the most common faults, typical repair costs, and the steps to take when your system stops performing as expected.

The most common solar panel faults

1. Inverter failure

The single most likely repair you will face. The inverter is the only component in a solar PV system with moving electronics that operate continuously for years. String inverters typically last 10–15 years, though some fail earlier; hybrid models and battery inverters are subject to the same wear. Replacement cost in 2026 ranges from roughly £500–£1,500 installed depending on system size and inverter type — a straightforward 3–4 kWp string inverter replacement runs £700–£1,100 including labour, while a hybrid replacement can reach £1,400–£1,800 installed. Signs of inverter failure include a blank or red-fault display, loss of monitoring data, and zero generation readings despite sunny weather.

2. DC isolator faults

A safety-critical component with a poor track record. DC isolators disconnect the solar array from the inverter and are required by UK wiring regulations. Government-backed research by the Building Research Establishment reviewed more than 50 solar PV fire incidents and found DC isolators were linked to 18 fires — the largest single source of PV-originated fires on the DC side. Root causes include moisture ingress, loose terminals, and incorrect crimps. If your isolator is making a buzzing or burning smell, switch off immediately and contact a qualified electrician. Many modern inverters now integrate the DC isolator internally, eliminating this weak point; if yours is a roof-mounted external unit and is over eight years old, ask your installer to inspect it.

3. Microcracks in solar cells

Usually invisible to the naked eye but detectable by specialist testing. Microcracks are fine fractures in the silicon cells caused by hail, foot traffic during installation or maintenance, thermal cycling, or manufacturing defects. They can reduce output by around 2–3% per affected cell and, if they progress, lead to hotspots. Electroluminescence (EL) imaging — where a small current is passed through the panel in the dark to reveal internal fractures — is the only reliable diagnostic method. If microcracks were caused by a manufacturing defect, they are typically covered by the manufacturer's product warranty. If caused by physical damage (hail, accidental impact), the claim routes through your home insurance rather than the panel warranty.

4. Hotspots

Localised overheating that can permanently damage a cell or trigger a fire. A hotspot forms when one cell or bypass diode fails and the surrounding cells force current through it, generating heat. Thermal imaging (infrared camera inspection) is the standard diagnostic: hotspots show as bright warm patches against the cooler panel surface. An IEC 62446-3 compliant thermal inspection provides documented evidence of faults, which is valuable for warranty or insurance claims. A single faulty panel can often be replaced; if bypass diodes have failed, the panel itself may need replacing rather than repairing.

5. Monitoring communication failure

Rarely a panel fault — usually a network issue. If your monitoring app shows no data but your generation meter is still ticking, the problem is almost always a Wi-Fi drop, router change, or firmware update rather than a hardware fault. Check your router is broadcasting on the 2.4 GHz band (most inverter dongles do not support 5 GHz), reboot the inverter, and check the manufacturer app or portal for reconnection instructions. No repair cost is typically involved.

6. Bird and pest damage to cabling

More common than most homeowners expect. Pigeons and squirrels frequently nest under rooftop arrays and can chew through DC cabling, leading to arc faults and potential fire risk. A pigeon-proofing kit — mesh skirting around the array perimeter — prevents nesting and is a worthwhile investment after any cabling repair. Cable repair costs vary widely depending on roof access but typically range from £150–£400.

7. Delamination

A warranty-grade defect. Delamination occurs when water penetrates between the glass, encapsulant, and cell layers of a panel, causing visible bubbling, yellowing, or browning. It accelerates cell degradation and, in severe cases, creates a shock or fire risk. Because delamination is almost always caused by a manufacturing defect rather than physical damage, it should be raised directly with the panel manufacturer as a product warranty claim.

What your warranties cover

UK solar panel systems typically come with three distinct layers of warranty protection:

• Manufacturer product warranty — covers manufacturing defects including delamination, cell cracking, and junction box failures. Most reputable manufacturers now offer 12–25 years of product warranty coverage; a small number of premium brands extend this to 30 years.
• Performance warranty — guarantees a minimum power output over time, typically ensuring panels retain at least 80–90% of their rated output after 25 years. This covers gradual degradation beyond the specified rate, not sudden failures.
• MCS workmanship warranty — under the Microgeneration Certification Scheme, all accredited installers must provide a minimum two-year workmanship warranty. This covers faults arising from the installation itself — poor cable routing, incorrect fixings, or roof leaks caused by the mounting system. MCS-certified installers are also required to provide an insurance-backed guarantee (IBG) so the workmanship warranty remains valid even if the installer ceases trading.
• Inverter warranty — manufacturers typically warrant inverters for 5–10 years, with extended warranties available for purchase. Check your inverter documentation; many manufacturers allow warranty extensions to be bought within a set window after installation.

What is not covered: storm damage, physical impact (hail above forecast severity, falling branches), and any damage caused by DIY modifications or work carried out by uncertified personnel. These are home insurance claims, not warranty claims.

Who to call

Start with your original installer. They hold the MCS installation certificate and are best placed to diagnose faults under your workmanship warranty. If they are no longer trading or unavailable, the MCS Find an Installer tool lists over 3,500 certified installers across the UK — search by postcode to find a qualified repairer near you. For manufacturer warranty claims, contact the panel or inverter brand directly; they will usually require the MCS certificate number and proof of purchase.

If you suspect a fault is covered by your home insurance — storm damage, for example — contact your insurer before arranging any repairs, as unauthorised work can invalidate a claim. See our guide to solar panels and home insurance for a full breakdown of what typical policies cover.

When to consider a full system upgrade

If your inverter has failed after 12 or more years, it is worth getting quotes for a replacement that also adds battery storage capability. A hybrid inverter swap — while more expensive upfront at £1,400–£1,800 installed — future-proofs the system for battery integration without rewiring the solar array. Read our hybrid inverter buyer guide to understand which models are compatible with your existing panels, and our string vs microinverter vs optimiser explainer if you are considering a switch in architecture at the same time.

Keeping repair costs low

The best way to reduce repair costs is early detection. Annual visual checks (look for discolouration, cracked glass, or loose fixings), monitoring your generation against expected output, and a professional inspection every five years will catch most faults before they become expensive. Keep copies of your MCS certificate, all warranty documents, and installation paperwork — you will need them for any warranty or insurance claim.