What is solar water heating?

Solar water (or solar thermal) panels trap the sun's heat in panels or tubes for use in homes, other buildings and swimming pools.  The solar panels are not obtrusive (it's similar to having a Velux skylight on your roof) and can either sit on an existing roof or be built into it.  They can either be professionally installed or you can do the work yourself. 

Solar systems usually give at least 20-30 years useful service, during which time the money saved more than repays the initial cost.  Solar panels are cost effective for heating swimming pools and for some industrial and agricultural uses, particularly where other energy sources are not available (warm water facilities on allotments for example).

There are two main types of solar collector:

• The flat plate collector - This consists of a metal plate to absorb the heat and tubes attached to it which contain the fluid for transferring the heat.  The metal plate is placed on a layer of insulation and the whole thing is put in a box with a glass or plastic lid.  These are the simplest and most efficient type of panel available.

• The evacuated tube collector - This works in a similar way to the flat plate collector but the heat absorber is enclosed in a vacuum to minimise heat losses.  These vacuum tubes look very similar to the tubes used in fluorescent light fittings.  They are somewhat more expensive than flat plate collectors.

How does solar water heating work?

A typical system consists of a heat collector, usually mounted on a roof.  It needs to face as near to south as possible (SE to SW is ideal).  Water is forced through the collector where it is heated by the sun, then through a coil in the hot water cylinder to transfer its heat to the surrounding water, where it is stored, ready for use.  There are only a small number of combination boilers that can be used with this technology, and they can be more expensive.  Here in Britain solar water heating can provide 50-70% of the water for a home, which spreads out to approximately 90% in summer, 50% in spring and 20% in winter. 

What are the benefits of a solar energy system?

Environmental benefits include reduced fuel consumption and displacement of fossil fuels.  A solar system would also add value to your home, and lower your energy bills as well as protecting you from increasing energy prices.

How hot does the water get?

On sunny days, temperatures of 70 to 90 degrees are common.  Even on cloudy days in winter some hot water will be produced as the system utilises energy from diffuse light.  In winter the system will pre-heat the water in your cylinder, meaning the solar system will make meaningful reductions to your gas, oil or electricity consumption throughout the year.  Also, as solar hot water systems are designed to store larger amounts of hot water than conventional systems, a correctly sized system will have hot water left over from the previous day. If you have a few cloudy days in a row the thermostat will turn the booster on to bring the water up to temperature.

What do I need to consider if I want a solar hot water system?

Solar systems operate best when:

• You have south facing roof space for the panels

• The roof space for the panels is unshaded by trees etc

• The panels are inclined approximately 30°-45° from horizontal

• The tank is properly sized for your longer term needs

How many panels will I need?

A typical installation for a family of four would need about 4 square metres of panels (usually two standard panels) - however, this may differ as it will be dependent on the optimal size of system for your property, the number of people in the house, capacity of cylinder installed, and available roof space.  Please note that it is possible to install a solar compatible tank now, and add the panels later when you can afford them.

Can I use solar panels on my existing system?

Probably. Most conventional hot water systems can have panels connected with a pump to circulate the hot water from the panels into the tank.

Can I use solar water heating for swimming pools?

Using solar water heating panels to heat a swimming pool is a particularly effective way to save energy.  Swimming pools can be expensive to run as a lot of energy is required.  With solar panels, the energy is free and the system can be left running continuously.  Moreover, swimming pools are mostly used during the summer months when the solar panels are working at their optimum even on overcast days.

For a swimming pool installation the number of panels needed is normally at least half that of the surface area of the swimming pool, depending on the system.  The panels are installed using the existing filter pump, and can be mounted on a roof or placed on the ground near the pool.

Will I need planning permission?

Not usually, as you are permitted to make certain minor changes to your home without needing planning permission, and installing a solar panel comes into this category.  These changes are called 'permitted development rights' - however, if you live in a listed building or in a conservation area you may need consent as these development rights do not apply.  We advise that you contact your local authority planning department for advice and also check if building regulations might apply.  If there are problems installing the panels on the roof, it may be possible to put a system in the grounds of your house.

How much does it cost?

The cost of a professionally installed system will vary depending on the size and type of the system, but prices range from around £2,000 to £3,000 with grant assistance.  A DIY installation would reduce this cost to around £1,500.  Unfortunately, some solar thermal installation companies sell their solar thermal systems through direct marketing techniques and frequently see systems at inflated prices of up to £8,000.

Please contact us for more information on prices and available grants.