Ourpower

Ourpower Guides - Heat Pumps - Details

Only a few metres below the ground the temperatures stays at around 11-12 degrees C throughout the year. Using ground source heat pumps (GSHP), this heat can be sourced to provide space heating in your home, and in some cases help pre-heat your water for your central heating system.

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Heat Pumps can also be used to extract heat from water (rivers, lakes) and from the air, although this is more suitable in warmer climates than the UK or for use to heat swimming pools.

Uses

Heat pumps are typically used as follows:

  • Providing all or a large part of the heating (space heating) required in a domestic house or business premises (typically using under floor heating since this type of heating is suitable for the relatively low water temperature produced).
  • Can be used for heating swimming pools.
  • Not ideal for providing hot water (from taps) due to relatively low water temperature.

How do Heat Pumps work?

Heat Pumps work by extracting heat from the ground (or from water or air), multiplying it and then using this energy to heat water. This is then typically used to circulate heat using a system such as under floor heating. Normal radiators could be used, but the size would need to be larger to take account of the lower water temperature that heat pumps produce as compared to an oil or gas boiler.

Heat Pumps are like fridges, in reverse. There are three important elements:

  • The ground loop, which comprises lengths of pipe buried in the ground, either in a borehole or a horizontal trench. The pipe is usually a closed circuit and is filled with a mixture of water and antifreeze, which is pumped around the pipe absorbing heat from the ground or water. An air pump simply extracts heat from the air.
  • The heat pump, which in the same way that your fridge uses refrigerant to extract heat from the inside, keeping your food cool, extracts heat from the ground or water.
  • A heat distribution system, which normally consists of under floor heating; but could include radiators for space heating and in some cases water storage for hot water supply.

The benefits - why install?

  • Heat pumps can be very efficient, particularly for new builds or when significant renovation is taking place.
  • Heat Pumps need to use electricity to power them, and are rated by their Coefficient of Performance (CoP). The CoP should be between 3 and 4, indicating that for each unit of electricity used, 3 or 4 units of heat are produced: an efficient system. Green electricity, Solar PV or a wind turbine could also be used to provide a carbon neutral complete system.

Is it suitable for my home or business?

Factors that need to be considered are typically:

  • You will need space outside your house (or a lake) for the ground loop.
  • For ground source, the ground will need to be suitable for digging a trench or borehole.
  • The type of heat distribution system. Ground source heat pumps can be combined with radiators but these will normally be larger than with standard boiler systems. Under floor heating is better as it works at a lower temperature.
  • Are renovation works, such as a new heating system, being implemented anyway? If so, payback can be very attractive.

An accredited installer or supplier will help you plan the best system for your circumstances and budget.

Installation, maintenance and costs

A typical ground source heat pump installation may cost around £1000 per kilowatt of peak heat output - this however does not include the cost of a suitable heating system in the property. Trench systems tend to be at the lower end of the range, boreholes at the higher end.
A typical 6 - 8kW system may cost between £6,500 - £11,500. This can vary with property and location. On average you can save £650 - £750 on your heating bills and 4.5 - 5.5 tonnes of C02 per year.
Grants are available - £1,200 or to 30% of overall maximum cost, but only for Ground Source Heat Pumps.

Where can I find out more?

The DTI funded low carbon buildings programme provides grants to help with the costs of installing heat pump technologies.
To be eligible for a grant you will need to use a certified installer and products.
Or visit the following sites:

Visit: Energy Saving Trust

Visit: Centre for Alternative Energy

Look for Ourpower Pioneers in the Ourpower Community who have fitted Heat Pump systems near you so you can ask and read about their experiences. Then use the Ourpower Directory to find local installers and suppliers - reading about what they can offer and what they have done, before asking a number to consider your situation and to quote. Always, get at least 2 quotes - more if possible.

To download in pdf format, click here.