What is solar O&M?
Solar O&M — operations & maintenance — is the ongoing work of keeping a photovoltaic installation generating safely, reliably and to standard once the installer has left site. Here's what it actually covers, where the terms get muddled, and the numbers it's judged on.
Generating is the easy part. Keeping it generating is O&M.
A solar PV system loses output the moment something goes wrong and nobody notices — an offline inverter, a tripped string, a failed optimiser, a soiled array. Those losses are silent. The panels don't make a noise when a third of a roof stops producing; the only signal is in the data, and only if someone is watching it.
Operations & maintenance is the discipline of catching those losses early, fixing them quickly, and proving — to the asset owner, the funder, the insurer — that the installation is being looked after to a recognised standard. For commercial & industrial (C&I) solar in the UK that usually means a contract with defined response times, periodic safety inspections, and a regular performance report.
People use "O&M", "monitoring" and "servicing" interchangeably. They're not the same thing — and understanding the difference is the difference between a contract you can defend and one you can't.
Monitoring, maintenance and compliance.
O&M is all three working together. Monitoring without maintenance is a wall of alarms nobody acts on. Maintenance without records is unprovable. Compliance without monitoring is a once-a-year snapshot that misses everything in between.
Knowing what's happening, now
Continuous data off every inverter — generation, power flow, string and device-level telemetry, native alarms. Monitoring is the data layer. On its own it tells you a site is down; it doesn't fix anything or prove you did.
Acting on it
The work itself: triaging an alarm into a case, dispatching an engineer, replacing a failed optimiser, cleaning, vegetation management, scheduled preventive visits. Reactive when something breaks, preventive on a calendar, condition-based when the data says so.
Proving it to a standard
Periodic verification against BS EN 62446-1, signed-off test reports, and the audit trail an asset owner or insurer can rely on. Compliance is what turns 'we keep an eye on it' into a defensible record.
A UK C&I O&M programme, end to end.
The exact scope varies with site size and contract type, but a commercial rooftop O&M programme almost always has these four moving parts.
Performance monitoring
Actual generation measured against a weather-corrected expectation, per site and per string. Open-Meteo irradiance and module temperature feed an expected-yield model so a dull week reads as a dull week — not a fault — and clipping on a bright day doesn't trigger a false alarm.
Fault detection & response
Deviations surfaced fast and triaged into cases with an owner and an SLA clock. Comms-stale, zero-production, low-power, inverter-offline, optimiser-drop and partial-offline conditions are caught in the next polling window, not at the next monthly review.
Periodic inspection (BS EN 62446-1)
Scheduled verification of the PV installation — insulation resistance, polarity, string I-V, earthing and protective devices — recorded against the standard, with photos and a signature, and filed against the site.
Reporting
A regular, client-ready record: generation vs expected, availability, open and closed cases, work completed, and any compliance documents. The artefact that shows the asset owner the contract is being delivered.
For more on the inspection side, see our practitioner's note on what auditors actually look for under BS EN 62446-1, and how SolarFleet turns a periodic inspection into a signed, filed report.
Three KPIs that run every O&M contract.
A good O&M report leads with these. They separate "the weather was bad" from "the system was underperforming" — and they're how a portfolio gets compared site to site.
Performance ratio (PR)
Actual output divided by the output theoretically possible for the irradiance and temperature the site actually saw. It strips out the weather, so it isolates how well the system itself is performing. A healthy UK C&I rooftop typically sits in the high 70s to mid 80s; a sustained drop points at soiling, shading, or a fault.
Availability
The share of time the system was able to generate when it should have been. It separates 'the kit was working' from 'the sun wasn't out' — the number an O&M contract's uptime commitment is usually written against.
Specific yield
Energy produced per kilowatt-peak installed. Because it's normalised by system size, it lets you compare a 200 kW rooftop against a 2 MW one — and benchmark sites across a portfolio on a like-for-like basis.
One site fits on a spreadsheet. A portfolio doesn't.
At two or three sites you can log into each manufacturer's portal in turn, eyeball the graphs, and keep a maintenance log in a spreadsheet. It works — just about. The trouble starts when the portfolio grows and the sites don't share an inverter brand.
Now you're switching between three or four monitoring portals that each define "alarm" differently, no two report the same way, and an underperforming string on a SolarEdge site looks nothing like one on a Solis site. Faults hide in the noise. Reports eat a whole Friday. And when a client asks "was the system actually available last quarter?", the honest answer is a shrug.
O&M software fixes the data problem first: one dashboard, every brand normalised to the same shape, weather-corrected expectations so alarms mean something, cases with SLA clocks, and reports that build themselves. It's the difference between O&M that scales with the portfolio and O&M that quietly falls behind it.
The economics are worth doing the maths on. See our breakdown of UK C&I O&M pricing benchmarks, or look at how SolarFleet's cross-brand monitoring handles a mixed fleet.
See solar O&M done in one place.
SolarFleet is solar O&M software built by InspireGreen, a working solar installer in Cardiff, and run on our own fleet. Connect a SolarEdge or Solis account and see one of your sites in the platform. Two sites are free forever — no card.