 SOLAR WATER HEATINGWritten by CAT's free information serviceemail: info@cat.org.uk; tel: 0845 3308373 or 01654 705989 Click here to download a printable version of this sheet (2 sides A4, PDF format, 50KB). Solar Water Heating or Solar Electricity? These are two very different technologies. To produce electricity you need 'photovoltaic' (PV) solar panels, which are a much more expensive option than solar water heating. See our information page on Photovoltaic Solar Power for details. How does solar water heating work? Solar collectors, or panels, are designed to absorb as much of the sun's heat as possible. They contain water, which once hot usually travels to a coil in a hot water cylinder and transfers the heat to the water there - known as an 'indirect' system. In 'direct' systems, water from the panels goes straight into the cylinder - these are generally unsuitable for areas with very hard water. Solar water heating panels should provide most of the hot water needs of an average household for the sunniest four or five months of the year. The rest of the time they will contribute to the heating needed. Over a whole year, about half of your hot water will have been heated by the sun. In most cases solar water heating panels will not provide space heating because there isn't sufficient sun in the winter, when you need heating most (although on a bright, clear winter's day they can make a welcome contribution). Some panels will need to be drained in the winter months to avoid frost damage. You can also use solar water heating for swimming pools. Why install a solar water heating system? Installing solar water heating has considerable environmental benefits and reduces the carbon dioxide emissions caused by burning fossil fuels. It's a really good way to make your home more environmentally friendly, and can also save you money - a properly installed solar water heating system should pay for itself within its lifetime. Is my roof suitable? Ideally, solar panels should be south-facing and free of shade, at an angle of between 20 and 50 degrees. Panels facing south-east or south-west will also operate efficiently. Rooftop panels are the most common, but they can also be mounted at ground level. You will need about 1 square metre per person. How will a solar panel feed in to my existing heating system? You need to have a conventional water heating system as well, such as a gas, oil or wood fired boiler (or even just a back-boiler on a wood stove), to top up the heat from the panels when necessary and provide hot water and space heating in the winter. If wood fuel comes from a sustainable source it will not contribute to climate change when burned, as the carbon dioxide released will be absorbed by replanted trees. You can add solar panels to most existing hot water systems, though you will usually have to add an additional 'pre-heat' water cylinder or change your existing one to a twin coil cylinder. You may need a pump to circulate the water, and some regulating equipment to prevent overheating. It is more difficult to use solar water heating with a 'combi' boiler because they are designed to take cold mains-pressure water, and solar systems supply hot or warm low-pressure water (although new modulating combi boilers will accept pre-heated water). Check with the boiler manufacturer or a solar engineer to see if your boiler is suitable. See our sheet on Solar Water Heating with 'Combi' Boilers for more detail. If your boiler needs replacing, a condensing boiler is the most efficient type. Condensing boilers are more expensive but the savings on fuel should compensate for the extra cost within a few years - and from then on you're saving money and fuel! Do also make sure that your cylinder is well-insulated, with a good thick cosy jacket. For further information our booklet Tapping the Sun is an invaluable guide to choosing and installing a solar water heating system, and describes how to choose a system that it right for you, and how it will fit into your plumbing system. How much will it cost? There are two main types of commercial solar water heating panel available - flat plate and evacuated tubes. Although evacuated tubes are more efficient they are also more expensive and if you spend too much installing a system you may not necessarily get your money back within its lifetime. (Though it would still have environmental benefits). You can compensate for the lower efficiency of flat plate collectors by installing a larger surface area. The cost of a commercial flat plate system, including installation, for an 'average' house ranges from about £2,000 to £4,000. Evacuated tube systems usually cost from £3,500 to £5,500. If the cost seems high check what it includes - for example, scaffolding can be expensive if your roof is hard to access (putting systems in to new buildings, or on new roofs obviously saves costs). To work out if a solar water heating system is worth installing from a financial point of view, you need a rough idea of how much you spend on hot water throughout the year, and when you use it. You can then work out how long it would take to get back your investment in solar panels. As electric heating is more expensive than gas, a solar water heating system will recover its costs more quickly if you have electric water heating. There are a few grants to help with the initial capital needed to install a solar water heating system. The Low Carbon Building scheme covers the UK, but there are sometimes local grants, which may be additional to the Low Carbon grants, or might be more generous. See below for contact details. So how do I get a system installed? There are lots of solar water heating installers around, so it is always worth getting a few quotes to compare prices. Don't be pressured into signing something by door to door salesmen or companies offering 'special discounts' - they may not offer as much of a saving as it seems. The Low Carbon Building programme installer lists (see below) are a good place to start. Or you could just look under 'Solar' in the Yellow Pages. Can I make and install panels myself? You can build and install your own DIY solar panels using old radiators or aluminium clip fins on copper pipes. These DIY panels can be installed for anything from around £500 upwards. We publish a booklet explaining how to do so, called Solar Water Heating: A DIY Guide (it's worth getting Tapping the Sun too, for information about how to fit it into your plumbing system). If you have good plumbing skills then you may be considering buying and installing a system yourself. However, you would not be able to claim a grant and you'd have to pay full VAT, so do think carefully about whether it is the best option for you. Further Information For details of all CAT publications, see www.cat.org.uk/catpubs For more on wood fuelled heating see our Wood Fuelled Home page. Detailed technical advice on the heating options available in your specific circumstances is available through CAT Consultancy. We also offers many residential courses, including one on solar water heating for householders, and another giving professional training to installers. We have many solar water heating systems on display at CAT, so you can have a look around these if you visit us. Remember that you can also You can also contact us at CAT's free information service with any further questions. Grants Low Carbon Buildings Programme Energy Saving Trust Solar for London Energy Saving Scotland Renewables Grants NIE Your Energy Trade Associations Solar Trade Association The Institute of Domestic Heating & Environmental Engineers (IDHEE) Association of Plumbing & Heating Contractors Chartered Institute of Plumbing & Heating Engineering
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. Personal recommendation is usually a good way to find an installer. Beyond this, membership of a trade body is a good sign of competence, as they will have certain codes of conduct. The Solar Trade Associationm, IDHEE and other organisations (see below) can provide lists of their members.