Solar thermal systems produce hot water. There are two principal types: evacuated tube and flat plate. Evacuated tubes tend to be more efficient, especially when the roof is not directly south-facing, but are more expensive. Flat plate can be mounted in the roof (rather than on top of the roof covering) and are therefore good for new builds. In an efficient house and used in conjunction with a good-quality cylinder and underfloor heating system, solar thermal systems can contribute to space heating as well as domestic hot water.
A typical domestic system will be 4m² to 6m², depending on the size of the property, and produce around 2,000kWh per year with a potential income of around £360 per year under the forthcoming Renewable Heat Incentive (tariffs yet to be confirmed). A typical domestic system will cost £3,000 to £5,000 (including installation and hot water cylinder) with a payback period of some 10-11 years.
The rules for buying solar thermal are largely the same as for PV. But solar thermal is likely to be working in conjunction with another system (i.e. a boiler or heat pump). The installer has to be capable of making the systems work together in harmony.
Your first port of call should be the Solar Trades Association (solar-trade.org.uk). There will be many solar thermal installers in every location to which, again, due diligence must be applied.
Alison and Andy Tombs installed solar panels as part of a bid to improve the efficiency of their home in Tyne & Wear.
Alison and Andy Tombs live in a terraced house in the Newcastle area with their two children. The family were previously reliant on a very large, unwieldy and inefficient gas-fired back boiler which took up a lot of space — it was about 20 years old too. Their fuel bills at the time were around £70 per month.
Whilst undertaking some work on their home anyway, they decided to look into renewable options for heating, and specified Worcester’s Greenskies solar water heating system which was installed in September 2007.
The installation took about two weeks to complete with the old boiler removed and the new Worcester Greenstar 18Ri system boiler installed, along with the new panels.
The majority of the home’s hot water is now supplied by the system and, during winter months, the new boiler kicks in to ensure a steady supply. The boiler is dormant during summer.
Alison says: “We are delighted with the results. There is a panel on the tank which tells us the water temperature — we know that if it’s over 43?C, we have enough for a bath as well as the washing up.
“Now we’re in winter, we are finding that the solar panels are heating the tank to between 20-30?C so we turn the boiler on for 30 minutes to an hour each day to top that up.”
Alison and Andy installed a Worcester Greenskies solar system (panels, cylinder and a new system boiler) at a cost of around £7,000 fitted.
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.
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.