Ground Source Heat Pump - Domestic

How efficient is a ground source heat pump system?

Modern systems can be 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 very dependent on the quality of the design and installation. The efficiency of the installation is improved by utilising solar recharge of the ground.

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. More powerful heat pumps for commercial buildings do not increase in size or price as much as they do in power output.

Can a GSHP supply hot water?

Yes. Some domestic systems are able to heat domestic hot water via a modern high efficiency indirect water cylinder.

Can GSHPs provide cooling?

Yes. Reverse-cycle heat pumps can deliver both heating and cooling very effectively. Cooling provided by heat exchange with cold ground is inherently more efficient than air conditioning which typically exchanges heat with hot air.

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.

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

Yes. All new houses in the UK are designed to meet Building Regulations and can 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.

Is a ground source heat pump system suitable for a poorly-insulated house?

Yes. Ground source heat pumps have been installed successfully in less well insulated houses and in Listed Buildings. If the building is not well insulated then a higher capacity heat pump can be specified or a heat pump with a higher temperature output can be installed. However, it is always wise to consider improving the insulation of building when a new heating system is installed as this may reduce the cost of the heating insulation - whatever kind of heating system is to be installed. 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. Is this a good idea?

Yes. Ground source heat pump systems are ideally matched to modern warm temperature underfloor heating because a heat pump transfers heat at a higher coefficient of performance if it delivers to a large warm water circuit (like underfloor heating) rather than a small high temperature circuit (like wall mounted radiators).

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

Yes, but the cost of a system is related to the heat losses, which will generally be higher in older buildings. Money spent on upgrading insulation levels can save on the capital cost of a ground source heat pump system.

Can radiators be used instead of underfloor heating?

Yes, but you may 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. If your house is not well insulated you will want to improve the insulation or install a heat pump capable of delivering higher water temperatures. Your installer will need to check the capacity of your radiators matches the heat output of the heat pump specified and the heat losses of your house. 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. This 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 for heat exchange with the ground 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 2 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?

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, therefore, no need for safety checks.

Are Ground Source Heat Pumps noisy?

No, a ground source heat pump makes less noise than a gas boiler, and very much less than an air source heat pump which drives a fan to extract heat from ambient air.

What about servicing and maintenance?

As with any valuable plant a ground source system should be covered by an annual maintenance agreement with the supplier. However, routine maintenace requirements are very low. A ground source heat pump can be expected to last over 20 years – longer than a combustion boiler – and the ground heat exchanger should have a life of over 100 years.

Ground source systems are automated. Because they come with low maintenance, low running costs, low noise and are out of sight, they are often referred to as "invisible heating systems".

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. Modern condensing gas boilers are more expensive to run at current gas prices, and 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.

Be careful to avoid judging an installation on price alone. It is more important to ensure you have a well designed system if your aim is to save money over the life of the installation.

Is Planning Permission required to install a GSHP?

No, a ground source heat pump installation is invisible, makes less noise than a gas boiler and issues no gases of any kind on-site: there is nothing for anyone to object to.

Are grants available to reduce costs further?

Yes, the government introduced Renewable Heat Incentive for ground source heat pumps installed in domestic buildings at 18.8 p/kWhr on 9 April 2014. Heat pumps installed before April 2014 also qualify for RHI (if commissioned after 15 July 2009).