Commercial Solar Panel Maintenance: What a Business Commits To

What maintenance commercial solar needs

Panels have no moving parts, which is why solar has a reputation for needing nothing. RC62 disagrees with that reputation: "All PV systems require a level of routine and preventative inspection and maintenance", and it says the system should be serviced and maintained to the installer's instructions and to BS EN IEC 62446-2, with a schedule that follows the service contract, warranty conditions or performance guarantees (RC62, 5.3.13).

RC62 notes that the system itself may not change over its 25 to 35 year life expectancy, but the things around it do: tree and vegetation growth, lichen, nesting birds and new construction nearby can all alter how it performs and add risk (RC62).

Inspections and electrical testing

RC62 refers to Solar Energy UK's operation and maintenance manual, which recommends inspecting commercial systems at least annually by a competent person, and to the IET code of practice, which covers scheduled maintenance, periodic verification and regular inspections (RC62, 5.11.1 to 5.11.2).

The testing that matters most for safety is on the DC side. RC62 says BS EN IEC 62446-2 recommends routine insulation resistance testing and string resistance testing, because rising resistance in a string can heat connectors and lead to arcing (RC62, 5.11.11). Thermal imaging, from the roof or by drone where roof access is not safe, is a cost-effective way to find failing panels; drone flights are governed by Civil Aviation Authority rules (RC62, 5.11.12, CAA).

Ask for a written report each year and keep it with the handover file. Your insurer may ask for it, and our guide to fire risk and insurance explains why.

Cleaning

How often panels need cleaning depends on the site: the tilt, nearby trees, birds, farm dust or traffic grime. RC62 says panels at a steeper pitch clean themselves to a degree but still need periodic cleaning based on a risk assessment; at lower pitches, such as many flat and low-slope industrial roofs, a scheduled programme should be in place. Ingrained dirt builds up along the bottom edge of each panel, and bird droppings stick at any angle and can cause hot spots (RC62, 5.11.8 to 5.11.9).

Who cleans matters as much as how often. RC62 says cleaning should only be done by people who understand the risks, that window cleaners are likely to lack knowledge of the fire and electrocution risks, and that panel cleaning companies should train their staff, work to a risk assessment and method statement and hold suitable liability insurance (RC62, 5.11.10). Roof work brings the work at height rules, and many industrial roofs have fragile areas such as rooflights and fibre cement sheets (HSE work at height, roof work). If your roof is fibre cement, see our guide to asbestos cement roofs.

Monitoring and spotting a fault

Every commercial system should have monitoring. RC62 says live online monitoring and error messages give easy access to operating data and early warning of problems, and that the IT department should be involved where the inverters have no internet connection (RC62, 5.11.6 to 5.11.7).

• Compare like with like. Output varies with the weather, so compare a month with the same month last year, or one inverter with another
• Act on error codes. An inverter that has tripped can stop generating for weeks before anyone notices the bill
• Watch for a slow decline. A string producing less than its neighbours points to shading, dirt or a fault
• Decide who gets the alerts. Someone on site, the installer, or an O&M contractor, with a named person responsible

O&M contracts: what to look for

RC62 notes that maintenance varies a lot with the size of the system, and that larger systems are likely to have a full-time maintenance contractor (RC62, 5.11.3). For a smaller system, a yearly visit from the installer with remote monitoring is common. Whatever the size, check:

• What is included. Monitoring, the yearly inspection, testing, cleaning, and whether parts and labour for repairs are extra
• Response time. How quickly they come out after an alert, and who decides it is urgent
• Warranty conditions. Some panel and inverter warranties ask for maintenance records; make sure the contract produces them
• Insurer's terms. The inspection and cleaning your insurer expects should be in the contract
• Reports. A written report after each visit, with test results
• Access. Who provides safe roof access, and whether that is in the price

Inverters and other parts that wear

Panels usually outlast everything around them. Inverters, DC isolators and connectors are the parts that fail more often, and they are where the 2017 BRE study found most PV fires started: DC connectors, inverters and DC isolators accounted for 84% of the PV system related fires it looked at (RC62). An IEC technical report cited in RC62 found that 33% of the PV fires it reviewed were caused by product failure.

Ask the installer which inverter they propose, what its warranty covers and for how long, and whether an extended warranty is available. Budget for replacing the inverter at some point in the life of the system, and keep inverters ventilated: RC62 says stored materials must not block them, because they produce significant heat (RC62, 5.3.12). Our guide to payback covers how running costs affect the return.