A typical installation should last approximately 2 days (for 2 engineers). This depends on factors such as complexity of roof installation, approach to roof etc. During the installation the disruption is kept to minimum and the hot water supply is normally back within a few hours.
Installations vary in price due to different circumstances such as roof complexity, loft access etc. However, as a guide, a typical installation for an existing 3-4 bedroom house should cost £3,000-4,500.

Government guideline is that flat plate collectors do not require planning permission (as long as it is not a listed building, or within a conservation area). Still, it is highly recommended to check with the local council.

The best output from a solar thermal system on an annual basis is when the collectors are facing due south inclined at 30 to 45 degrees to the horizontal. However, even if the direction deviates from due south, the output will still be reasonably good (see reference chart from Germany), in which case a lower inclination is advised (this can be fixed with appropriate fittings).
If the house has east-west roof split, the installation can still achieve good results through a larger area of collectors, putting separate collectors on each side and picking up the sun in the morning and the evening on each side.
 

The systems can be fitted to most houses. Unless there are extreme circumstances (e.g. no roof space), the only important factor is the direction of the roof.

The answer varies greatly and depends on many factors. These factors include type of energy currently used (e.g. oil, gas, electricity), the cost and quality of the system and cost and quality of the installation, as well as other parameters.

We have run the analysis to show the payback period for a typical household. The period of payback is 8-12 years ON AVERAGE (which means that it will vary both up and down, subject to the specifics of the household).

Furthermore, our systems have the following added benefits which improve the payback return:

• Our systems all come with a built in immersion heater, which can be set to bypass the boiler completely, thus making it appropriate for flats without a boiler, and make it more cost effective.
• Our systems can also be connected to the central heating system, thus providing pre-heating energy savings on sunny winter days.

Another important savings is the environmental angle: environmentally, a system's CO2 savings are impressive; the average household can save half a tonne of CO2 emissions per annum.

A schematic diagram is attached below. Solar water heating systems consist of a panel, usually mounted on the roof, which is designed to absorb heat from daylight. When there is sufficient daylight, water is pumped through the panel to the hot water cylinder and back in a closed continuous loop.

As the heated water passes through the solar coil in the hot water storage cylinder, the heat is transferred, via a heat exchange coil, to the surrounding water in the tank. It is this water in the tank that is then used in the showers, sinks and baths. This is known as an indirect system because the water that is used is heated indirectly by the solar energy.

The existing method for heating water (e.g. gas-fired boiler or electric immersion) acts as a backup for when there is insufficient sunlight. The system works automatically. The customer will always have hot water at the required temperature, whenever they want it. In summer, almost all hot water needs are met by the solar system, the rest of the year it pre-heats the water so the boiler only tops up to the required temperature.

The collector is made up of a metal sheet (copper) called the absorber plate to which a selective surface coating has been applied allowing for very efficient heat absorption (i.e. it gets very hot!). Copper pipes are soldered to the back of the absorber plate. The pipes and the absorber plate are then placed in a well-insulated box and covered by a hardened low-iron glass which has a coating that allows for good light absorption and low light emissivity.

As water is circulated through the solar panel, heat is transferred from the absorber plate to the water, which is then circulated through the system to the hot water cylinder.

The UK receives slightly more than half of the solar energy received at the equator, definitely enough to operate a solar water heating system. This varies depending on where you are in the country, with better returns in the south (see chart below). A typical solar water heating system in the UK provides 50% - 60% of annual domestic hot water requirements. This is spread out over the year to approximately 90% in summer, 50% in spring, and 20% in winter. A solar system provides heat input even on cloudy days by utilising energy from diffuse light. In winter the system will pre-heat the water in the cylinder, meaning the solar system will make meaningful reductions to the gas, oil or electricity consumption throughout the year. The solar water heating system works alongside the existing hot water system. On cloudy days, the little sunlight there is will preheat the water in the cylinder - and the boiler or immersion heater will do the rest.

UK solar irradiation - Annual Total kWh/sq.m

See chart above. In broad terms, households in the north will require larger collectors to achieve the same level of energy as in the south. As a rule of thumb, a household in the north of the country will require 3 collectors of 2 sq.m each for a 200 litre cylinder (compared to 2 such collectors for a household in the south).

Yes. For example, if the original installation was for hot water supply only, the customer can later 'upgrade' and have it connected to central heating, under-floor heating etc.

There are predominantly two sizes of kit that should address the needs of most households in the UK:

• 4-6 people household - 200 litre cylinder, 2 x collectors of 2 sq.m each;
• 6-8 people household - 300 litre cylinder, 2 x collectors of 2.6 sq.m each.

With more grants available now than ever before there has never been a better time to install a solar water heating system. The Department of Trade and Industry is offering grants of £400 through their Low Carbon Buildings programme, however, there are additional grants from local councils. For example, some of the 31 London Boroughs who have signed up as partners to Solar for London are offering Solar Rewards up to £1,500 (cash discounts) in addition to the DTI's grant.

The process for grant application is fairly simple, and normally requires sending your installation quote to the council for approval and them activating the installation. The grant arrives by post within a short while. For further information visit: www.lowcarbonbuildings.org.uk.

The system is listed on the "Clear Skies" list of approved systems making it valid for DTI grants. The system has tested and passed the highest European standards (BS EN12975), which are the key criteria for getting the "Clear Skies" approval. In addition, the system has tested successfully at many European test centres (e.g. TUV Germany, SPF Switzerland, ENEA Italy).

The warranty is

• 10 years on solar collectors;
• 5 years on hot water cylinders;
• 1 year on solar station (pump etc.);
• 1 year on electric immersion heater (inside the hot water cylinder).