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Green energy systems

​Solar hot water panels

Solar water heating systems use free heat from the sun to warm domestic hot water. Solar collectors, usually mounted on a roof, are designed to absorb the suns energy, often reaching high temperatures. Water is pumped through the collectors in order to cool them down, resulting in hot water, which then feeds into an insulated hot water store.


  • Hot water throughout the year
  • Sunlight is free, so once you’ve paid for the initial installation your hot water costs will be reduced.
Solar hot water ‘evacuated tubes’ on roof

Solar photovoltaic panels / Wind turbine

  • ​If you currently generate electricity for your home from solar panels or a wind turbine, you can now divert some of this electricity that isn’t being used in your home to your immersion heater. This means you can heat your water free of charge.
  • This will require a small gadget called a ‘power diverter’ (available from several companies in the UK), costing around £250.
  • In addition electricity generated from renewable energy sources qualifies for financial help from the government under the ‘Feed in Tariff Scheme’. Unfortunately the government has recently cut this tariff which reduces the incentive to purchase a system.
Small scale home wind turbine

Heat pumps

A recent growth area in electrical heating is ground, air and even water source heat pumps. They can be up to 300% more efficient than a conventional boiler.

Ground Source Heat Pumps (GSHPs)


  • Ground source heat pumps typically reach temperatures of around 50°C, which is significantly lower than with a boiler, which can reach a temperature as high 90°C (although it’s recommended that you set the temperature at around 65°C). So, you will need to run a heat pump for longer to achieve the same level of comfort, and it tends to work better with underfloor heating, rather than radiators. Although much more expensive to install, they can be as cheap to run as gas central heating and are certainly a good option to consider if you live off the gas network.


  • Could lower your fuel bills, especially if you replace conventional electric heating.
  • Could provide you with income through the government’s Renewable Heat Incentive (RHI).
  • Can heat your home as well as your water.
Ground source heat pump diagram

Air Source Heat Pumps (ASHPs)


  • Air source heat pumps absorb heat from the outside air.
  • This heat can then be used to warm water for radiators or under-floor heating systems, or to warm the air in your home.
  • The CoP (Coefficient of Performance) of air source pumps is 2:1 and just like a ground source system can be connected to wet central heating or warm heating systems.


  • Lower fuel bills, especially if you are replacing conventional electric heating
  • Potential income through the UK government’s Renewable Heat Incentive (RHI)
  • Efficiently heat your home as well as your water
Air source heat pump diagram


Biomass is the word used for the wood material (wood pellets, chips or logs) used for heating.


  • This type of heating is a feasible option if you live near woodland or you have access to waste wood, otherwise it can prove to be expensive.
  • A wood fuelled biomass boiler could save you hundreds of pounds a year compared to electric heating
Biomass burner diagram.

Solar heating

Many homes receive unobstructed sunlight even during the cold season, such homes can opt for solar heating. This is one of the cheapest forms of alternative energy and you can either buy a manufactured system or build one of your own. These systems make use of solar energy to heat liquid or air, then this heated substrate is transferred through a storage system inside the rooms or alternatively transferred directly into the interior space.

Solar gain

Sunlight passing through windows naturally heats internal areas. Solar gain, as it’s called, is often forgotten as a heat source. To take advantage of solar gain, a home needs large south-facing windows and smaller windows to the north.


  • When combined with ‘thermal mass’, solar gain can have a further beneficial effect on reducing the use of other fuels to heat your home.
  • Using a similar principle to storage heaters, the capacity of exposed bricks or concrete to hold warmth can be put to positive use. Floors and walls made of these materials will absorb heat when the indoor air is warm or there is direct sunlight falling on them. Later, when the indoor air is cooler, they will release the heat back.


  • Solar gain and thermal mass are of course free, but capturing it may require major refurbishment. Some advanced eco-homes rely on super-insulation and heat coming from sunlight, occupants and as a by-product of using electrical equipment.
Solar gain diagram

Hydro technology

These micro hydropower systems use running water to generate electricity. Whether it’s a small stream or a larger river, they all flow downhill. Before water flows down a hill, it has potential energy because of its height. Hydro power systems convert this potential energy into kinetic energy using a turbine, which drives a generator to produce electricity. The greater the height and the more water there is flowing through the turbine, the more electricity can be generated.


  • A hydro system can generate electricity 24 hours a day, often generating all the electricity you need and more.
  • If eligible, you can receive payments from the Feed-in Tariff for all the electricity you generate, as well as for any surplus electricity which you can sell back to the grid.
  • Excess electricity can be used to provide cheap heating and hot water for your home.
  • A low cost option for off-grid homes.
Micro hydropower system diagram. With some systems the generator can be placed directly in the water flow.