Solar Thermal Panels

Professional advice & installation in and around the Chichester area

Solar water heating (known as solar thermal) systems capture the free heat from the sun and use it to heat up water for use in the home. It’s a simple process:

  • panels on your roof absorb heat from the sun – they are known as the collector
  • the water in the panels heats up
  • this hot water is pumped through a coil in your cylinder
  • which transfers the heat to the water in the cylinder

Is solar thermal suitable for my home?
The ideal situation for solar panels is facing due south, although they are effective facing anywhere between south east and south west. As a rule of thumb you need between 1 and 2 m2 of collector (solar panels) per person living in the house. Shade on the panels at any time of day will reduce the performance.

Most panels are mounted on a roof, but they can also be mounted at ground level. It is important that they get direct sunlight. To get the best results they should be at an angle between 20 and 50 degrees from horizontal (most pitched roofs fall within this bracket).

If you have an electric shower it won’t use your solar hot water. Similarly cold-fill dishwashers and / or washing machines heat the water they use. In this situation, solar water heating is not suitable unless you use the bath for most of your washing and bathing, as you won't be able to use much of the solar hot water you generate.

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Solar panels are compatible with most existing hot water systems. However, you will need a new cylinder with two coils. Ideally it should be big enough to hold two days worth of hot water. Solar hot water with combi boilers is more difficult, but still possible. If you have a combi boiler it is important to check with the manufacturer that it will accept pre-heated water.

If your present system is gravity fed, it will need a control (such as a valve and pump) for the hot water circuit so the panels can work effectively in winter when the boiler is running for central heating.

What does solar thermal cost?
The cost of installing solar a solar thermal system will depend on the type and quality of the panels, whether you need scaffolding, and how easy it is to integrate into your existing plumbing system.

As a guide, average systems are likely to cost between £3,900 for a two person household to £5,000 for a six person household according to the Solar Trade Association. But every installation is unique which is why we offer a free no obligation site survey and quotation.

The cost of scaffolding and the new cylinder are both significant, so a cost- effective time to install would be when you need a new hot water cylinder, or when you are having repairs done on the roof (or at the same time as a solar PV installation).

How much hot water from solar thermal panels?

Solar thermal panels should provide most of your hot water from April to September, and make a worthwhile contribution in the months on either side of that period. Outside of that estimates vary depending on who you ask. The Energy Saving Trust field trials found that solar thermal panels will provide about 60 per cent of a household's hot water needs, if well-installed and properly used.

How much you benefit will depend on a variety of factors:

  • How much hot water your household or business uses. The higher the usage, the more benefit you get from a solar thermal system.
  • How much interest you take in how the system works and adapt to make the most of the free hot water (ie having showers in the evening rather than the morning). The sun isn’t as reliable as a timer clock.
  • The size of your cylinder. Many cylinders only hold enough water for a day’s supply of hot water, so a day or two of cloud and rain will mean you have to turn on the boiler or immersion heater.
  • How you programme your back up heating. If your control panel does not allow you to programme the hot water and central heating separately, you may not get the maximum benefit from the solar panels when the heating is turned on. By only boosting the hot water once the sun has gone down, you maximise opportunity for solar heating.
  • Adequate insulation of both cylinder and pipes carrying hot water.
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What type of solar thermal panel is best?
There are two types of solar thermal panel: flat plate panels and evacuated tubes. Flat plate panels consist of an absorber plate in an insulated metal box. The top of the box is glass or plastic, to let the sun’s energy through, while the insulation minimises heat loss. Lots of thin tubes carry water through the absorber plate heating it up as it passes through.

Instead of a plate, evacuated tube collectors have glass tubes containing metal absorber tubes, through which water is pumped. Each tube is a vacuum (the air is ‘evacuated’ hence the name), which minimises heat loss.

Field trials have found little difference in performance between the two. For many people the decision is a matter of aesthetics.

Planning permission for solar panels?
Solar panels are generally considered ‘permitted development’ in England and Wales as long as they do not protrude more than 200mm from the wall or above the roof slope; and are not higher than the highest part of the roof.

They are permitted in a conservation area as long as the panels are not installed on a wall that fronts a highway. However, if you live in a listed building you will have to apply for planning permission. Up-to-date advice is available on the government’s planning portal.

Stand alone solar is permitted development as long as it is less than 4m high, more than five meters from the boundary, and the surface area of the panels does not exceed nine square meters; or any dimension of its array does not exceed three meters. In a conservation area, it must not be nearer to the highway than it is to the dwelling. If it is in the grounds of a listed building you will need to apply for planning permission.

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