What is solar water heating?

Solar hot water systems comprise a number of solar panels (collectors) and can be either 'direct' or 'indirect' systems. Within an indirect system, the water contained within the panels travels to a coil in your hot water cylinder and the heat is transferred to the water within the tank. This is the most common type of system. A direct system is one where the solar-heated water within the panels is transferred directly to the inside of the cylinder. These systems are not suitable for areas with very hard water.

The technology

Solar hot water panels are usually one of two types: flat plate or evacuated tube. Evacuated tubes are around 15% more efficient than flat plate systems however they are also more expensive, meaning that it will take longer to re-coup your investment. Installing flat plate panels with a larger surface area can compensate for their lower efficiency, at a reduced cost compared to installing an evacuated system.

Solar water heating systems usually provide most of a household's hot water requirements for much of the late spring, summer and early autumn months. The panels do still work in the colder months of the year (even on cloudy days), and will still be able to provide some of your hot water needs during the winter. Solar hot water systems are unlikely to provide a significant contribution to meeting the space heating needs of your home. This is because your heating demand is highest in the winter months and although the panels still work during the winter, the shorter days and increased cloud cover mean that the system will be unable to meet the demand. It will still make a contribution, particularly on a sunny winter’s day. Some panels may need to be drained in the winter months to avoid frost damage (an approved installer will be able to advise you on this matter). Most indirect panels contain antifreeze. Although they do not need draining they do require regular maintenance and change of antifreeze – in a similar way to your car.

The ideal location for solar panelling is a mounting facing south and free from shade (e.g. from a chimney or large trees). Panels facing southeast or southwest will also work efficiently. Solar water heating installers will be able to advise you on the most suitable location for your panels.

In addition to your solar hot water panels, you will need to keep your existing water heating system to act as a 'top up' when necessary and to provide most of your hot water and space heating supply during the winter. Most existing hot water systems can be used in conjunction with solar hot water systems, however to ensure the system works effectively you may need to add certain items such as an additional cylinder. The installers who provide the quotes will be able to advise you on any additional equipment that you might need and this should be included in the cost of your installation.
If your boiler is a 'combi' boiler it may not be suitable for connection to a solar water heating system or may require you to install a hot water storage cylinder inside your property. This is because they are designed to take cold mains-pressure water whereas solar systems supply hot or warm low-pressure water. However, new modulating combi boilers do accept pre- heated water. It is always advisable to contact the manufacturer of your boiler to find out its suitability or ask the advice of the solar engineer when the estimate is being produced.

Boilers are now rated with an A-G system for their energy efficiency credentials with A being the highest. If you are advised by an engineer that your boiler needs replacing it is a good idea to think about installing a boiler with an A rating. Choosing an A-rated boiler may be slightly more expensive, however the reduced fuel demand (due to the increased efficiency of the boiler) will mean that your extra investment will be returned within a few years.

Life span and warranty

Solar hot water systems generally come with a 10-year warranty and require very little maintenance. It is advised that you check your system once a year and arrange for a more detailed inspection by a professional installer every 3-5 years. It is advisable to ask the installer about the warranty and maintenance requirements of a particular system before you decide which quote to choose.

Cost

The Department of Trade and Industry currently give average system prices as £2500 to £4000 for a flat plate system, and £3500 to £5500 for a system containing evacuated tubes.

Contact Details

South Derbyshire District Council
Energy Officer
Civic Offices
Civic Way
Swadlincote
DE11 0AH

Tel: 01283 228719
email: energy@south-derbys.gov.uk

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