Solar Thermal Hot Water Systems

Solar Thermal Energy (STE) is a technology which can be used to convert solar energy from the sun into hot water for homes.

Solar Thermal Energy differs from photovoltaics because it does not convert solar energy directly into electricity. Instead, solar thermal collectors concentrate the light from the sun to create heat. This heat is used to run a heat engine which turns a generator to make electricity.

Solar thermal collectors are typically installed on the roof of a property and can either consist of flat plates or evacuated tubes. The solar thermal collectors heat a fluid which is then pumped to a special twin-coil hot water cylinder via pipes. The heated fluid in the cylinder heats the household water to a temperature of up to 60 degrees, where it is stored until needed.

A conventional boiler or immersion heater can be used to make the water hotter, or to provide hot water when solar energy is unavailable.

Solar thermal diagram

Benefits of Solar Thermal Hot Water

The main advantage of solar thermal hot water is a reduction in your hot water costs.

  • Save money on your fuel bill.
    Your fuel bills will come down as solar thermal hot water systems typically provide up to 70% of a property's domestic hot water requirements.
  • Low payback time.
    Solar thermal hot water systems are covered by the government's Renewable Heat Incentive (RHI). Payback periods can be as little as 5 years. Systems can be expected to work for in exceess of 30 years.
  • Green Deal finance.
    Solar thermal hot water systems are an eligible measure under the government's Green Deal, so you may be eligible for help paying towards the installation costs.

Flat Plate Collectors

Solar thermal flat plate collector

Flat plate collectors look more like traditional solar panels. They have a flat, glazed, dark-surfaced absorber plate which contains metal tubing. The plate covering the tubing absorbs the solar energy and the casing stops heat from escaping from it. A fluid is constantly run through the tubing which is heated up by the solar power captured from the sun.

Evacuated Tube Collectors

Evacuated Tubes

Evacuated tube collectors look very different. The panel comprises of an array of glass tubes in a parallel row, which contain an absorber insulated by a partial vacuum. They are proven to be more effective throughout the year than flat plate collectors, but are also generally more expensive.

Flat Plate Collectors vs Evacuated Tube Collectors

The choice between flat plate and evacuated tubes comes down to a number of factors.

  • Cost.
    A typical flat plate panel system will cost approximately 25% less than an evacuated tube system.
  • Application.
    Flat plate panels are better for heating when you have a heat pump or for pre-heating large hot water tanks. Evacuated tubes are better able to reach higher temperatures when the weather is cold, so are more suitable for smaller hot water only syatems.
  • Asthetics.
    Many people feel that flat panel systems are better looking.

Take the guess work out of getting the right system. Our expert advisors can help you work out which system is best for your needs.

Evacuated tubes close up

Is my property suitable for a Solar Thermal Hot Water System?

Solar Thermal panels can be installed on most properties, providing there is sufficient un-shaded roof space facing West, South West, South or South East. Typically you will need 3m2 to 4m2 to locate the collector panels.

You need to have space for a larger, or an extra, hot water cylinder, as we will usually need to replace your existing cylinder, or add a dedicated cylinder with a solar heating coil.

We will also check that your current boiler is compatible with solar thermal hot water. Most conventional boiler and hot water cylinders are, but our expert advisors will be able to confirm that you have compatible technology.

Call Greentec Now!

The best time to go for renewable energy is right now. The early adopters have gotten better tariff rates which are index linked and can last for 20 years. To find out how much you could save/earn from renewable energy, simply give us a call.


1. Call Us

Call Greentec on 0333 456 5000 to arrange a FREE consultation with one of our renewable energy experts. We come to you, at a time that suits you.


2. Your Consultation

Our experts will listen to your requirements, survey your property and make recommendations to get you the best solution for your circumstances.


3. Your Solution

If our recommendation ticks all the right boxes, then we're in business. We help you at each stage of the process to ensure you get the right system quickly and at the best price.