Operations and maintenance

Buying the system right is half the job. Keeping it right is the other half. Panels soil, connectors loosen, an inverter throws a fault, a string drops offline, and on a roof nobody walks across, all of that can sit unnoticed for months while the asset quietly underperforms. The point of an O&M service is to catch the slow drift and the sudden fault early, so a long-life asset behaves like one across its full design life.

Our O&M is built on three things working together: planned maintenance and inspection on a schedule, continuous performance monitoring so a problem surfaces early rather than at the next quarterly bill, and a handover that hands you a twelve-month defects-rectification period and an Insurance-Backed Guarantee behind it. This is about resilience and sustained performance, rather than a saving we can promise you in advance.

Monitoring tells you the system is generating. It does not tell you that a DC connector is starting to arc, that a cable clip has failed, or that a string is being shaded by something that has grown since commissioning. Those are physical faults found by physical inspection, and on a commercial roof they carry a fire and a revenue risk, so they belong on a schedule rather than a hope.

A planned visit covers the parts of the system that monitoring cannot see. Field-made DC connectors are a recognised weak point in rooftop PV, so the joints, the glands and the enclosures get checked for heat and water ingress. Earthing, bonding and surge protection are verified against BS 7671 rather than taken on trust. And the settings audit catches the quiet revenue thief: an export limit drifted from the G99 agreement, or a CT clamp reading the wrong way, both of which cost generation without ever flagging as a fault.

• Physical inspection of panels, cabling, isolators, inverters and any battery units for condition, heat and degradation
• Connector, gland and enclosure checks at the known PV failure points
• Earthing, bonding and surge-protection verification to BS 7671
• A settings and configuration audit against the G99 connection agreement
• A written report with photographs and a prioritised list of actions

Monitoring and a settings audit catch the electrical drift. The other half of an O&M visit is the physical condition of an array that nobody walks across between visits, and on a real commercial roof a recognisable set of problems turns up again and again. The visit exists to find them while they are cheap, before they show up as lost generation on a bill or, worse, as a fire risk.

Soiling, and why a shallow-pitch or coastal roof needs more cleaning than a buyer expects. Cleaning is a larger part of a commercial O&M plan than most buyers assume, and the sites that need the most of it are the ones a buyer expects to need the least. A shallow-pitch array does not let rain sheet the dirt off the way a steeper domestic roof does, so soiling settles and stays, and output drifts gently down without ever flagging as a fault. A coastal site compounds it: salt in the air plus more airborne soiling means the glass dirties faster and rain clears less of it. We do not put a fixed cleaning frequency on a page, because the right interval is set by how your roof actually soils, read off the monitoring trend and confirmed at the visit, rather than off a generic calendar. Where soiling is the dominant loss on a site, the detail of how and how often we clean is covered in the commercial solar cleaning guide.

Bird fouling, dead birds and the shaded cells they leave behind. Droppings and dead birds sitting on the modules are a routine find on a commercial roof, and they are not only an aesthetic problem. A fouled patch of glass soils like any other soiling, but a concentrated droppings deposit, or a carcass, shades the cells beneath it, and a shaded cell in an otherwise generating string runs as a hot spot that, left long enough, can damage the module. The visit clears the fouling and inspects the cells underneath for the heat damage it may already have caused.

Shattered and cracked modules. Modules break. Impact from debris or a dropped tool, hail, thermal cycling over the seasons and the microcracks that propagate from it all leave a panel cracked or shattered, and a damaged module can keep generating while it quietly underperforms and lets water in at the failure. Identifying the affected panels and replacing them is part of putting the array back to its design output. This is also where independent monitoring and a periodic performance audit earn their place: a single failed or cracked module rarely announces itself, and the audit is how the underperformance gets traced back to the panel that caused it.

The problem we see most often that buyers least expect sits in the gap underneath the array. Pigeons and gulls nest in the space between the modules and the roof, and in doing so they pull the DC cabling out of its clips. That is a genuine electrical fault in its own right, an unsupported DC cable chafing on a roof or sitting in standing water, and under the thinking behind RC62 it is exactly the kind of DC-side condition that becomes an arc and ignition risk on a live array that cannot be switched dead in daylight. Nests, debris and fouling building up under the panels add to it.

An O&M visit checks the under-panel cabling for clips that have been pulled or displaced, re-secures the runs and clears the nesting material that drives the problem. Where birds are a persistent issue on a site, the durable answer is perimeter bird-proofing: a pigeon or critter mesh clipped around the edge of the array to close off the gap so birds cannot get under the panels to nest in the first place. It is a fitted commercial measure that removes the cause of the cabling-pull fault rather than re-clipping the same cables visit after visit. Whether a roof warrants it is a survey-led judgement about how exposed the array is and how much bird pressure the site sees.

Sentinel is our sister platform: a free, independent monitoring app from the same group of companies that watches the system's performance and tells you when it drops. The job it does is simple and it matters more than it sounds. Without it, the first sign of a fault is usually the bill, by which point you have already paid for the generation you did not get. With it, an underperforming string, an inverter error or a system that has dropped offline surfaces while it is still a small problem.

It is independent by design. It is not tied to one manufacturer's portal and it does not depend on us selling you anything to keep watching. That matters because a finance director should be able to see the truth about an asset without it being filtered through the people who installed it. When Sentinel flags something the maintenance schedule has not yet reached, the fault gets attention early rather than waiting for the next planned visit.

Monitoring finds the fault and inspection prevents most of them, but equipment does occasionally fail, and when it does you want the diagnosis right the first time. That work sits with Solar Tech Support, the group's independent, brand-agnostic diagnostics and repair arm. It is the team that fixes orphaned systems whose original installer walked away, which means it is built to work on equipment it did not install rather than only the kit we put up.

What that buys you on a bad day is a diagnosis rather than a quotation. The fault is traced to the component that caused it and the report names that part, so a failed inverter channel is not answered with a proposal to replace the array. Where the failure turns out to be a manufacturer defect the warranty position is established as part of the same visit, because the commissioning record and the equipment schedule have been held since handover rather than reconstructed after the event, which is what usually decides whether a claim succeeds.

O&M scope is set by contract rather than by a regulated standard, so the same three letters cover everything from an annual photograph of the inverter to a properly scoped programme of inspection, monitoring and agreed response. Two agreements at the same rate can therefore be worth wildly different amounts to you. The label tells you almost nothing; the clauses tell you everything. A sound scope names the work, names how often it happens, and names what lands on your desk afterwards. Read for each of these by name and treat an absence as a question rather than an assumption.

• Monitoring, and who is contracted to act on it. What is watched, how alerts are raised, and whose job it is to respond. Monitoring nobody is obliged to act on is a dashboard rather than a service.
• Inspection, at a stated frequency. A physical visit at a named interval covering the panels, cabling, isolators, inverters, earthing and any battery units, because those faults are found by hand rather than through a portal.
• Electrical testing, referenced to a standard. The periodic verification the asset needs to stay safe and compliant, written against the standard it is carried out to rather than left implied.
• Cleaning, assessed rather than assumed. Set against how your roof actually soils and how it is accessed, so nobody is billing to clean a roof the rain keeps clean.
• Fault response. What happens when something breaks, on what terms, and at whose cost.
• Reporting. A written record after each visit, so the asset is documented and you can see what was done.

Two further splits decide what you are actually buying. The first is preventive against corrective work. Preventive maintenance is the planned work that stops faults happening, it sits on a calendar, and a fixed annual fee normally covers it. Corrective maintenance puts a fault right once it has occurred, and contracts diverge sharply there: some include corrective labour to a stated limit and charge parts and major component replacement separately, others include a diagnostic visit and quote the repair once the cause is known. Neither approach is wrong, but an agreement that looks cheap on the preventive line can carry an open-ended corrective bill behind it. The second is the term. Read the initial period, the renewal basis and the notice you must give to end it together, because an attractive rate locked to an auto-renewing multi-year term with a long notice window is a different commitment from the same rate on an annual one.

Warranty obligations are the part buyers most often miss. Manufacturer warranties on panels, inverters and batteries usually carry conditions: maintenance carried out and recorded, settings kept within stated limits, faults reported within a window. A contract that does not keep those conditions met can quietly cost you a claim years later, when a component fails and the paperwork will not support it. Treat a headline uptime percentage or a fixed response time advertised before anyone has seen your site with caution, because a figure that has not been scoped to your asset may not survive contact with it. What matters is that the terms are named, agreed and yours, which is why the cleanest moment to put a contract in place is at handover, and why an inherited system waits for no anniversary: the contract starts once the scope is settled.

The panels and the mounting structure are commonly rated for 25 to 30 years or more. The inverter is not. String and central inverters are the shortest-lived major component, typically rated for around 10 to 15 years, with standard product warranties commonly running 10 to 12 years and extendable, at a cost, to roughly 20 to 25 years. Financial models for a solar asset routinely budget for at least one full inverter replacement over the project life, commonly modelled somewhere around year 10 to 15.

The honest framing for a finance director is that this is the single largest planned mid-life capital cost on the system, and it should be sinking-funded rather than treated as a surprise. The exact timing and cost depend on the specific inverter, how hard it is run and how the contract handles replacement, so we put no fixed year or figure on it. The principle is fixed: budget for the replacement from the start so it is a planned event rather than a shock to the model. The design sets which inverter goes in, the O&M plan sets how its end of life is funded, and the work itself runs through inverter replacement, brand-agnostically, when the day comes.

Every install is delivered under a JCT or NEC contract, and the handover is a formal part of it, rather than a set of keys and a goodbye. You receive the commissioning data, the test certificates to IEC 62446-1, the as-built records and the operating information, so the asset is documented from day one and the people running the building know what they have.

The contract carries a twelve-month defects-rectification period: if a defect in the work appears within that period, we come back and put it right at our cost. Behind that sits an Insurance-Backed Guarantee, so the cover does not rest solely on us still being here to honour it. That is the assurance that matters above 50 kWp, where MCS does not apply: the named engineering stack and a real contract you can hold us to, rather than a domestic badge.