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Solar Maintenance · sub-service

Solar PV Fault Diagnostics & Repair UK 2026

Reduced generation, RCD trips, alarm codes — every solar fault has a root cause. Here is how we diagnose and fix the common ones, with realistic 2026 prices.

Updated 6 July 20266 min readReviewed by Steve Moran

The most common solar PV faults

  • Underperforming string — usually one shaded panel, a degraded MC4 connector or a hot-spot on the panel itself. We isolate by string current measurement during peak generation hours.
  • Inverter alarm codes — most resolve with firmware update, a single component swap or RMA via the manufacturer.
  • Earth fault — usually a chafed cable on a roof penetration. We trace using a megohm meter and repair without removing panels where possible.
  • RCD trip — typically a moisture ingress at a DC isolator. Replacement and resealing fixes it.
  • Battery underperformance — capacity test against the original spec; manufacturer warranty claim if applicable.
  • SEG meter not reading — usually a smart-meter pairing issue with the supplier rather than a system fault.

Typical 2026 fault diagnostic costs

Pricing is bespoke per site — talk to our consultants. Get a tailored quote →

When KMM is on call

Customers on our Premium service plan get priority response within 5 working days for any reported fault. Standard plan customers get 10-working-day response. Without a service plan we work to 15-working-day response and a £140 call-out fee.

FAQs

How can I tell if my system has a fault?
Check your monitoring app — generation noticeably below the previous year for the same month is the first sign. Listen for inverter beeping or look for amber/red status lights. If the inverter display shows an error code, photograph it before calling us.
Can I diagnose remotely?
Often, yes. If your system has Wi-Fi monitoring and we have remote access (you grant this at install or service start), we can diagnose most faults remotely. Many do not require a site visit.

Request a Fully Funded Electrical & Structural Survey

Tell us about your roof, your bills and your goals. KMM runs a fully funded electrical & structural survey, designs a system, runs the numbers and tells you honestly whether solar makes sense for you. No deposit, no pressure.

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