Solar Water System FAQs

How reliable are solar hot water systems?

A government survey was conducted and a sample of 700 solar water heating systems analysed. The main findings were:

• Solar systems can work reliably for 20 years or more.
• There is little if any difference between current system performance and that when the system was new.

Why install a solar hot water system?

Installing a solar water heating system has considerable environmental benefits and reduces carbon dioxide emissions caused by burning fossil fuels. It is a really good way to make your home more environmentally friendly. It can also save you money - a professionally and properly installed solar water heating system should pay for itself inside 15 years on fuel bill savings alone. Not to mention the increase in the value of your house by up to £5,000 and extended boiler life of up to 60% as a result of installation. Government grants are also available.

How much does a solar hot water system cost?

As a rough guide you can expect a solar hot water system to cost around £5,000 depending on the size of your house and your hot water demand.

Does it have to be sunny all the time?

There is a common misconception that solar water heating is ineffective in the UK for climatic reasons. Whilst it is clearly not as effective in the UK as it could be in Spain for example, a good modern system will make a significant contribution to water heating requirements. For example a well-designed system should provide 50-75% of annual domestic hot water requirements.

What happens when it is cloudy, raining or snowing?

It is important to point out that solar water heating systems work off diffuse radiation as well as direct radiation from the sun. This means that the system will still work in such circumstances when the weather is cloudy, raining or snowing. The only time when the collectors' operation would be interrupted is if a layer of snow is covering them for any length of time.

How much hot water will it provide?

A solar water heating system 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 overall requirement, which is subject to the requirement of the property. Typically between 50% and 75% of the hot water requirement can be met by having a solar water heating system.

How many solar panels will I need?

Roughly speaking you will need about 1 square metre of solar panel per person. For an average residential domestic installation usually 4m2 to 5m² of flat plate collector are required or 3m² of evacuated tube collectors. Regarding cylinder capacity, the general rule of thumb is approx 50 litres of capacity per person.

How will a solar water heating system feed into my existing heating system?

A conventional water heating system, such as gas, oil, or wood fired boiler, will be required to top up the heat from the panels where necessary. Solar collectors can be added to most existing hot water systems and all you need to do is replace the existing storage cylinder with a twin-coil cylinder to take advantage of a solar primary circuit. However systems are designed on an individual basis and we encourage a site survey before progressing to installation.

How big are the collectors?

The collector (panel), together with the glazing and insulation are generally mounted in a box that is usually coloured grey or black and typically 1 to 3m² in area and are visually akin to a large roof window.

What is the optimum installation location?

Ideally solar collectors (panels) should be south facing, free of shade and at an angle of 20 and 50 degrees. Collectors facing south-east or south-west will also operate efficiently. More rarely, collectors can be mounted on a freestanding tilted a-frame on the ground or a flat roof and even onto walls as a last option. Increasingly, collectors are becoming available that can be incorporated into a new or existing roof in much the same way as proprietary roof windows; in any case collectors rarely project above the existing roofline.
Connecting pipework is normally run from the back of the collector directly through to the roof void, and is normally not visible from the exterior of the building.

Are there grants available?

For information on the grants available to community projects concerning the installation of solar hot water heating systems, click here.