Frequently Asked Questions

How efficient is a ground source heat pump system?

Modern systems are very efficient. For each kilowatt of electricity used to run the heat pump, three to four kilowatts of heat can be delivered to the building. The efficiency of a GSHP installation is dependent on the quality of the design and installation.

Are ground source heat pumps new?

GSHP systems are common, particularly in the USA, Canada, Sweden, Switzerland and Germany. The principles of ground source heat pumps were first described by Lord Kelvin in the 1850s and continuous development since they were first used commercially more than 50 years ago has greatly improved their efficiency and reliability. They now provide a proven, cost-effective, safe and environmentally friendly alternative to fossil fuels.

How large are ground source heat pumps?

A heat pump for a house is about the size of a large fridge.

Can a GSHP supply hot water for a house?

Yes. Some domestic systems are able to heat domestic hot water via a modern high efficiency indirect water cylinder. An immersion heater can boost the temperature which can be done at night using off peak rates.

Can GSHPs provide cooling?

Yes. Reverse-cycle heat pumps can deliver both heating and cooling very effectively.

Can a standard domestic electricity supply be used?

Yes. Heat pumps are designed to run on a standard UK single phase supply. However, a three-phase supply is a preferable option, and will be essential for larger installations.

Would a ground source heat pump system be suitable for a well-insulated house?

Yes. Almost all new houses in the UK are designed to meet Building Regulations and should be able to benefit from a ground source heat pump. Building Regulations have been designed to conserve fuel, reduce heat losses and ensure greater energy efficiency, in order to ensure that all modern properties need less heating. For a well-insulated building the size of heat pump will be smaller, will need smaller ground loops and will therefore be less expensive. You should take advice from an installer with experience.

My architect suggests I install underfloor heating in my new house. Is this a good idea?

Yes. Ground source heat pump systems are ideally matched to modern warm temperature underfloor heating.

I have an older property. Can a ground source heat pump be installed?

Yes, but your building must be well insulated for you to gain most benefit. The cost of a system is directly related to the heat losses, which will generally be higher in older buildings. This can add substantially to the cost of installation. Money spent on upgrading insulation levels can save a considerable amount on the capital cost. Some older buildings may never be made sufficiently energy efficient to use a modern heating distribution system such as warm temperature underfloor heating, or warm temperature radiators.

Can radiators be used inside my house instead of underfloor heating?

Yes, but you will need larger radiators, sized for the typical 45°C to 50°C water temperatures obtained from efficient GSHP systems. If your house is well insulated they may be suitable. Your installer will need to check how big they would have to be and the space they would take up. Modern die cast aluminium radiators are very efficient and smaller than conventional radiators. Upstairs is usually less of a problem as bedrooms are normally kept at lower temperatures.

Can the heat pump be installed outside or in a car-port, garage or basement?

Yes. There normally means the pump will be nearer to the pipe connections to your ground loops, which often makes the whole system easier to connect.

Will long trenches have to be dug on my land for the ground loops?
My land is too rocky to dig trenches – can I still fit a heat pump system?
I don't have enough land to dig long trenches – what do I do?

Vertical boreholes can be used instead of trenches.

How big are the trenches?

A typical heating-only installation for a medium sized, new build detached house would need two narrow trenches, each 300 mm wide and 40 to 50 metres long and 1.8 metres deep. The trenches can be straight or curved and laid in any direction to suit your site, providing they are five metres apart. A standard excavator can dig the trenches and backfill them after the ground loops have been installed. Your installer would be able to do this work and plan it to ensure the minimum of disruption to your site. Once the ground loops are installed, pressure tested and buried, your renewable energy collection system should need no further attention. However, its location needs to be recorded to avoid it being accidentally disturbed!

Can trenches be installed on a downward sloping site?

Yes, provided the trenches can be dug, a moderate downward slope is not a problem. Consideration needs to be given to purging air from a system with ground loops higher than the heat pump.

I have a large plot of land but the ground is quite hard. Can a shallower trench be dug?

Yes, the ground loop coils can be laid so that the coils lie horizontally in the trench rather than vertically. This would need a wider but shallower trench depth to at least 1.2 metres. However, this is not as satisfactory as a deep trench in which the coils are vertical and you will need a special slinky configuration and probably longer trenches. Your installer will be able to advise you accordingly.

I have some very wet land. Can I use this?

Yes, wet land is better at conducting heat so, as long as a trench can be dug, it is ideal.

I have a large pond. I have a stream. Could this be used?

Yes, it is possible to use very large ponds and fast flowing streams as a heat energy source using an open loop system.

Are GSHP systems environmentally friendly?

Yes. In the UK, there is now a strong move towards alternative technologies that are sustainable and environmentally much more acceptable. 40% of CO2 emissions are derived from the heating of buildings. By using renewable sources of energy to heat your property you can help to reduce these carbon emissions, particularly when compared to burning fossil fuels such as oil. Most electricity suppliers are now offering 'clean green' electricity from a renewable energy source and, if you use this to power your heat pump, your property will be totally heated from renewable energy with zero carbon emissions.

Are Ground Source Heat Pumps dangerous? What about servicing and maintenance?

There are no hazardous gas emissions, no flammable oil, LPG or gas pipes, no flue or chimney and no unsightly fuel tanks. GSHP systems have absolutely NO site emissions. There is no need for safety checks and routine maintenace requirements are very low. A ground source heat pump can be expcted to last over 20 years – longer than a combustion boiler – and the ground heat exchanger should have a life of over 50 years.

How do running costs compare with conventional alternatives?

In a modern, well insulated house, a ground source heat pump can offer very high efficiency and low running costs. An oil-fired boilers cost considerably more to run, and electric heating is at least three times as expensive. A modern condensing gas boilers may only be a little more expensive to run at current gas prices, but gas prices are set to rise. Also, all fossil fuel boilers need regular servicing to maintain efficiency and check safety.

What are the costs?

The initial purchase costs of a ground source heat pump system are more than a conventional oil or gas fired boiler. The initial capital expense is offset by lower running costs, lower maintenance and low servicing requirement. There is also the security of knowledge that the majority of your heating and cooling energy comes out of your ground, is under your control and will not increase in price.

Are grants available to reduce costs further?

Yes. See Renewable Heat Incentive.