How to look after your solar panels to maximise returns

The lack of moving parts means solar PV is a low-maintenance option compared with other technologies, but systems cannot be forgotten about once installed.

Keeping panels clean is an obvious requirement, but there are a host of other issues to consider, from overhanging trees shading panels to vermin damaging wires, all of which can dramatically reduce system performance and may go unnoticed without regular monitoring.

“It’s amazing how many people don’t monitor system generation regularly,” says Bev Bambrough of Loughborough-based electricians C Gascoigne, which has compiled a list of solar PV issues to be aware of (see below).

Potential solar PV problems

• Inverter failure – Often indicated by LED lights or fault code.
• Panel failure – Physical damage (broken glass, water ingress) or electrical failure (eg. cell failure, damaged connectors).
• Inverter mismatch – Oversized inverters may be slow to start in morning and shut down early in evening. Undersized inverters may stop or be permanently damaged by high voltage.
• Shading – Position panels to avoid shade and remove overhanging vegetation.
• Dirt, leaves, bird droppings – Particular issue on ground-mounted or low-pitched panels where rainwater cleaning is insufficient.
• Poor installation – Potential issues vary widely; for example,connectors not installed properly to loose wiring connections.
• Overvoltage – Supply fluctuations can cause inverters to trip out where grid electrical supply voltage is close to the upper limit. Inform your DNO.
• Undervoltage – Rare, but similar result as overvoltage.
• Inverter overheating – Excessive heat can cause inverters to cut out. Locate in a cool place and keep cooling fans free from obstacles.
• Panel overheating – Not a major issue in UK conditions.
• Faulty electrical supplies – Regular supply problems can cause inverters to cut out and may not be related to the PV array.
• Panel cell degradation – Varies across manufacturers, but typically 1% a year.

Source: C Gascoigne

“Most people take quarterly meter readings for the Feed-in Tariff (Fits), so that is an easy way to keep an eye on what’s generated and compare to what was forecast.

“Lower than expected performance could indicate a problem, if it’s not due to the weather.”

Inverter failure is the biggest cause of problems, while solar panel modules, many of which come with warranties covering the 25-year lifespan, are rarely at fault, she says.

Wiring problems are another issue to watch out for, particularly where squirrels or other vermin chew wires.

With inverters typically costing several hundred to over a thousand pounds, they are the most expensive part to replace and warranties typically last five to 10 years.

Maintenance contracts

The nature of PV installations means maintenance and repairs must normally be done by a qualified electrical engineer.

However, installers usually leave written details of any maintenance checks that owners need to do and will often set up an operation and maintenance contract for the first year after commissioning.

This typically includes meter checks, Fits and export contract management, fault and warranty management, including repairs or replacement parts.

Other tasks such as cleaning and electrical inspections may be contracted separately, says Strutt & Parker energy engineer Joseph Vitolla.

It is usually down to the system owner to arrange future O&M contracts, which are commonly negotiated every 12 months, he continues.

The level of service and cost varies depending on site characteristics and involvement of the system owner, so it is worth getting a breakdown of quotes before selecting a contractor, he says.

For a typical 50kW rooftop array, Mr Vitolla says annual costs range from £400 for a basic operation contract (for example, meter readings, monitoring and fault management) to £1,500 for full operation and management of the system, including cleaning, roof access equipment, annual or biannual electrical testing and Fits and export contract management.

Doing some tasks in-house, such as submitting meter readings and Fits administration, or providing roof access equipment, can help reduce costs, he notes.

Use a reputable provider

Plenty of firms offer O&M services for solar PV, but Mr Vitolla recommends using the installer as the first point of contact. If they cannot offer the services required, ask them to recommend another trusted company, he says.

There is no specific accreditation scheme for solar PV maintenance so only Microgeneration Certification Scheme (MCS) approved contractors should be used, he adds.