Ground Source Heat Pumps (GSHPs)

ground source heat pump matched with underfloor heatingPipes are buried in the garden to extract heat from the ground. The temperature underground stays relatively constant around the year and Ground Source Heat Pumps take advantage of this stable source of heat.

A GSHP circulates a mixture of water and antifreeze around a loop of pipe – called a ground loop – which is buried in your garden. Heat from the ground is absorbed into the fluid and then passes through a heat exchanger into the heat pump.

This heat can then be used to heat radiators, underfloor or warm air heating systems and hot water in your home. Due to their low temperature output and efficiency range, ground force heat pumps are better matched to underfloor heating than to radiators in the home.

The length of the ground loop depends on the size of your home and the amount of heat you need. If garden space is limited, a vertical borehole can be drilled instead.

The benefits of Ground Source Heat Pumps

Ground source heat pumps can heat your home and provide hot water and:

  • could lower your fuel bills (heat pumps are run by electricity)
  • could provide you with an income through the government’s Renewable Heat Incentive (RHI)
  • could lower your home’s carbon emissions (heat pumps need electricity to run so they have some impact on the environment, the heat they extract from the ground is renewed naturally)

Heat pumps deliver heat at lower temperatures so they need to be working over longer periods than boilers, during the colder weather they may need to be running constantly. If heating radiators you will notice they are not as hot as when heated by a boiler.

Air source heat pumps can be easier to install than a ground source heat pump, though efficiencies may be lower.

How do GSHPs work?

Natural heat from the ground is absorbed into a fluid inside a loop of pipe buried underground (ground-loop). The heat is transferred to a refrigerant by the evaporator, changing it from a liquid to a gas. The compressor compresses the gas, causing the temperature to rise. The condenser then transfers the heat from the hot gas to the central heating system to heat water for the heating and hot water circuits of the house. The cooled ground-loop fluid passes back into the ground where it absorbs further energy from the ground in a continuous process as long as heating is required.

Is a Ground Source Heat Pump suitable for me?

Is your garden suitable?  

Do you have suitable garden space for a ground-loop and  is it accessible by digging machinery. Normally the loop is laid flat or coiled in trenches about two metres deep, but if you are short of garden space you can install a vertical loop down into the ground to a depth of up to 100 metres.

Is your home well insulated?

Since ground source heat pumps work best when producing heat at a lower temperature than traditional boilers, your home needs to be well insulated and draught-proofed for the heating system to be effective.

Best if replacing electric or coal heating

The system will pay for itself much more quickly if it’s replacing an electricity or coal heating system. Heat pumps may not be the best option for homes using mains gas.

What type of heating system will you use?

Ground source heat pumps are best suited to being matched to underfloor heating systems or warm air heating due to their low temperatures slow constant heating nature rather than with radiator-based systems because of the lower water temperatures required.

Is the system intended for a new development?

Combining the installation with other building work can reduce the cost of installing the system.

If you want an accredited GSHP installer to assess your home and help you choose the best setup to meet your needs call Steven Banks on 01462 636376

What are the typical costs, savings and earnings of GSHPs?

Costs

Installing a typical system costs between £9,000 to £17,000.

Running costs will depend on the size of your home and how well insulated it is.

Savings

How much you can save will depend on what system you use now, as well as what you are replacing it with. Your savings will be affected by:

  • Your home heating system – Underfloor heating is more efficient than radiators because the water doesn’t need to be so hot. If underfloor heating isn’t possible, use the largest radiators you can.
  • Your fuel costs  – Heat pumps use electricity to run, but you will save on the fuel you were using to heat your home/water.  The more expensive the fuel you are replacing the more likely to make a saving.
  • Your old heating system – If your old heating system was inefficient, you are more likely to see lower running costs with a new heat pump.  
  • Water heating – If the heat pump is providing hot water then you are likely to need to top this up with other heating sources. 
  • Using the controls effectively – You will probably need to set the heating to come on for longer hours, but you might be able to set the thermostat lower and still feel comfortable.

These are the savings you might make every year when replacing an existing heating system in an average three-bedroom semi-detached home with a typical GSHP installation and a good installation:

Existing system

   

Ground source heat pump 
performing at 250%

Ground source heat pump 
performing at 300%

Gas

£/year

Carbon   dioxide/year

£0

350kg

£130

800kg

Electric

£/year

Carbon   dioxide/year

£480

4,820kg

£610

5,270kg

Oil

£/year

Carbon   dioxide/year

£180

1,180kg

£310

1,640kg

Solid

£/year

Carbon   dioxide/year

£200

4,950kg

£330

5,410kg

A zero saving means it could cost you just as much to run the heat pump as the system you are replacing. Assumes average boiler efficiency for each fuel type; heat pumps produce more energy (as heat) than they use as electricity, so their efficiency is more than 100%. Source – Energy Saving Trust

Earnings

You may be able to receive payments for the heat you generate using a heat pump through the government’s Renewable Heat Incentive (RHI). This scheme should be launched in Summer 2013. 

From August 2011, you may be able to get help with the installation costs of a ground source heat pump through the Renewable Heat Premium Payment scheme. 

What maintenance is required for Ground Source Heat Pumps?

Typically GSHPs come with a 10 year warranty and are expected to operate for 20 years or more, however they do require regular scheduled maintenance. They will require an annual check by you and a more detailed check by a professional installer every 3-5 years.

The Ground Source Heat Pump Association say that there is no need for safety checks for ground source heat pumps and that routine maintenance requirements are very low. These may include pre-heating season checks of the water pump, external pipes and fittings and electronics.

Do I need planning permission for GSHPs?

In England, Scotland and Wales, domestic ground source heat pumps are generally allowed as permitted developments, but check with your local authority to find out whether you need planning permission or not.

If you want an accredited GSHP installer to assess your home and help you choose the best setup to meet your needs call Steven Banks on 01462 636376