Solar PV systems produce electricity. There are two main panel types: monocrystalline and polycrystalline. ‘Mono’ are more efficient – and more expensive – and often a bit smaller than equivalent ‘poly’ systems. Poly can be up to 20% cheaper – and for larger roofs may, therefore, be more financially attractive for some – but will produce less electricity than an equivalent rated mono system.

A typical domestic system of 4kWp will cost somewhere between £8,000 - £12,000 — a big outlay, so it’s essential to ensure you are choosing the right product and installer. Here’s some tips to ensure you don’t end up disappointed:

  • Check the supplier: do they have a good record? Take up references, speak to their former clients and check out the work.
  • Use only MCS-accredited suppliers and equipment. The MCS scheme is run by the Government and both the equipment and installer must be accredited for the system to qualify for Feed-in Tariffs. See for more details
  • Check out the price. Most reputable suppliers are coming in under £3,000/kWp for systems from 2kWp to 4kWp. Much more than that should ring alarm bells.
  • Do your homework on Feed-in Tariffs — do not rely on the supplier to explain it all to you. Check that the amount you will get back justifies your investment.
  • Use only brand name panels. With manufacturers like Sharp, Schüco, Kyocera, Solar Century and Romag, you know it will be a quality product that will last for decades.

Case Study

Karl and Jane Godden have been living in Norwich with their 3kW PV system since June 2010. Supplied by Anglian, who they used on account of a previously good experience buying windows, the system cost around £12,000 to install and generated £1,400 of income under the FiTs scheme in its first full year (the Goddens signed up at a lucrative early stage of the scheme). “What’s more, we’re saving 20-30% on our electricity bills,” explains Karl. “We’ve introduced little lifestyle changes, such as using the dishwasher during the day rather than overnight, to get more benefit from the amount of electricity the panels produce.”

A Few Things to Bear in Mind

PV arrays are denoted as kWp. That is the peak output in kilowatts. A 4kWp array will produce 4kW output only in ideal conditions — on a bright, cloudless day. For the rest of the year it will produce somewhat less.

A detailed guide to solar photovoltaics (PV). Includes advice on installation, the different types of panels, costs, and case studies.

The bigger the system, the lower the unit cost. The reason being that the ‘infrastructure’ – cabling, scaffolding, the inverter, etc. – costs pretty much the same whatever the system size (up to 4kWp).

The average electricity production across the UK for good-quality panels is some 800kWh per 1kWp. So a 4kWp system will produce around 3,200kwh per year. Actual production will vary with the site and with the quality of the panels.

Consider the power demands of various pieces of household equipment and the fluctuating output with passing seasons, and that we use most equipment in the evening, and we quickly see that the proportion of production we can actually use in the house is quite small. The figure used is typically 50% but that may not always reflect reality.

PV panels degrade over time. Actual production can fall by more than 20% over 25 years (the duration of the FiT scheme).

PV panels take around 20 years to recover the CO2 emitted during their production. In both financial and CO2 terms PV is a long-term investment.

Expert Tips

Ploughcraft, manufacturer of the Solar-Log, Britain’s first solar PV log system, offers its top tips for choosing a solar panel installer (01484 723344)

Make sure you choose a company that employs all its own roofers and electricians. This will ensure that your installation is of the very highest quality.

Ask to see the installer’s qualifications — many companies are using unqualified staff.

Ask what roofing experience the installer has — many solar companies have no roofing expertise at all and this is a crucial skill. It’s a bonus if they have an NVQ in solar roofing with heritage experience.

Choose a company which has hundreds of installations under its belt and that is happy to provide customer testimonials.

Ask who guarantees the workmanship and ensure it is underwritten in case the company goes bust. Reputable companies offer a solar care insurance warranty for ten years.

Ask who is going to check the structural integrity. It is not unusual for installers to miss the fact that the solar panels may overload the roof structure.

Installation Issues

Richard Swords, MD of PV supplier Greenenviro Energy Systems (0800 064 6014), explains the installation process.

Residential installations rarely take longer than two days, and the panels can be fitted on virtually any type of roof — it’s the roof’s condition that matters. It has to support the panels and their roof anchors and rails; if the structure is too weak, the installation can’t go ahead.

The best time to install the panels is when your property is being built or re-roofed, as the rafters are exposed and it also gives you the opportunity to have recessed panels, for a flush fit. Keeping the roof watertight is critical, so disruption to the tiles and felt is kept to an absolute minimum. Some tiles will need to be removed, so that the roof anchors can be screwed to the rafters at specific intervals, and are then replaced. The position of the roof anchors is important: if they are inaccurately placed, the rails, which sit on top of the tiles, will not be parallel and the panels will look uneven.