What a solar service costs, and how often you actually need one

The short answer

Three different things get sold under the word maintenance and they cost different amounts. A diagnostic call out to find a fault runs roughly £80 to £150. A routine inspection and performance check runs £80 to £250, and a full annual plan sits between £150 and £495. A repair is quoted separately after diagnosis, and the one most likely to land is a replacement inverter at £700 to £2,000 fitted.

The frequency question has a published answer that almost nobody quotes at you. The MCS solar PV installation standard, MIS 3002 Issue 6.0, carries a maintenance schedule in Appendix F. For a privately owned domestic home it advises visual checks by the customer once a year, an intermediate visit by an MCS contractor every 10 years, and a full visit with test equipment every 15.

What is actually in a service

A service is a checklist, and the checklist is public. This is each tier of the MCS schedule, the closest thing the UK has to a specification for what you are buying.

Source: MCS MIS 3002 Issue 6.0, clause 7 and Appendix F, dated 18 March 2026. Frequencies are advisory and apply to a privately owned dwelling. Rented, public and commercial buildings carry shorter intervals.

Read the third column and you can see where the money in an annual plan goes. Every test needing equipment you will never own sits in the 15 year tier, so an annual visit largely repeats checks you could make from the garden with your monitoring app open. The written report does have value as evidence, because a manufacturer asked to honour a long warranty will want proof the system was looked after.

Servicing, cleaning and repair are three separate purchases

• Servicing is an inspection against a checklist. It finds problems and produces a report, and plans including labour normally cap it at an hour or two.
• Cleaning is a window cleaning job with roof access attached: about £100 to £160 with an inspection, £120 to £180 for a deep clean.
• Repair is priced per fault after diagnosis. No maintenance plan obliges the company to carry one out for free.

What fails, and what each fix costs

Panels are rarely the problem. The clearest published picture of which components go wrong comes from the government's evidence on PV fires, gathered by BRE, and it points at the connections rather than the glass. Across 80 UK incidents in that database, DC isolators were the probable point of origin in 26, more than every other component combined. DC connectors accounted for 5, inverters 6 and PV modules 2. On root cause, poor installation practice was probable in 21 cases against 6 for a design error and 3 for a faulty product.

The mechanisms it lists are mundane: moisture in connectors, junction boxes and switches, badly crimped contacts, incompatible plugs mated together, plugs never pushed fully home, loose screw terminals. That is what an intermediate visit looks for, and it is a better argument for booking one than any yield figure.

From UK cost guides published July and August 2026. Ranges are national, with London and the South East at the top of each band.

Bird damage is the fault most often ignored until it is expensive. Nesting material blocks the ventilation gap, guano attacks frames and etches glass, and pigeons peck at DC cable and connectors, which puts you back at the top of that fire list.

Telling a real drop from a dull month

Almost every worried call about lost output is a homeowner comparing this month with last month. UK generation swings by more than three to one across the year, so the only reading worth acting on is this month against the same month a year ago.

These are modelled monthly figures for one kilowatt peak of south facing panels at a 35 degree pitch in the Midlands, from PVGIS, the same source behind our county pages.

PVGIS v5.2, SARAH3, modelled at 52.5N 1.5W, 35 degree pitch, due south, 14% loss. Annual total 983 kWh per kWp. December comes in under 30% of July on a healthy system.

A plain string system reports one number for the whole array, so a failed module hides inside the total until it is severe. Optimisers and microinverters report per panel, which is the difference between knowing something is wrong and knowing which panel is wrong. The trade offs are in microinverters, optimisers and string inverters compared.

What a third party doing the work does to your cover

• Manufacturer product warranty. Covers the part failing and survives a competent repair by another firm. What it rarely covers is the engineer, the scaffold or the diagnostic time, so a free replacement inverter can still arrive with a bill attached.
• Manufacturer performance warranty. Pays only when measured output falls below a published curve, so the claim rests on monitoring evidence. Keep the data, and keep any maintenance log.
• Installation team workmanship warranty. This is the one that actually breaks, and it covers fixings, roof penetrations and wiring. Installation teams routinely write in that unauthorised work ends the cover, with abrasive cleaning and drilling module frames for bird mesh as the classic self inflicted versions.

If the original installation team is still trading and still liable, call them first even when someone else is cheaper, because keeping the workmanship cover intact is worth more than the £100 you save. If they have gone, ask any MCS-certified firm to confirm in writing that the work will not affect cover you still hold.

When replacing beats repairing

• The repair approaches a third of a new system. A 4 kW installation runs around £6,500 to £8,500 in 2026, so a £2,000 inverter on a 4 kWp array from 2012 is close to the line, and replacing buys newer panels and fresh warranties.
• The modules are obsolete. Once a panel cannot be matched, one failure means mismatching the string or replacing the array, and a roof carrying early modules no longer in production is usually worth doing properly rather than patching.
• You want a battery anyway. If the inverter is due, a hybrid unit at £400 to £600 more avoids paying for the same job twice.
• The VAT treatment differs. The zero rate on installing energy saving materials in residential accommodation runs to 31 March 2027, then reverts to 5%. A replacement sits inside that relief, a standalone repair may not, so get the VAT stated on both quotes.

One exception cuts across all four. If the system still receives Feed in Tariff payments, get your licensee to confirm in writing what changing the installation does to them before anyone quotes. On a 2012 system that is often worth more than the hardware.

Clearline gives independent guidance and never installs. Work is carried out by an MCS-certified installation team for your area, and this page exists so you can tell a genuine fault from a plan you do not need. If replacement is on the table, the 2026 cost guide has the current figures.

Checked August 2026. MIS 3002 Issue 6.0 is dated 18 March 2026 and applies to installations certified from 18 June 2026. Repair prices are national ranges from UK cost guides, not quotations.