A ground source heat pump (GSHP) extracts heat from the ground.
(Read more about how heat pumps work here.)
However, installing them isn’t always straightforward.
Because of space limitations, vertical borehole drilling is often needed.
When boreholes are needed
The first consideration for ground source heat pumps is space. This dictates what type of system you install.
A horizontal ground source system
The system circulates a solution through pipes or loops, which absorb underground heat and filter it through a heat exchanger into the pump.
It is used if there is enough available outdoor space to install shallow trenches, about 1.2 metres deep.
It does not use boreholes.
A vertical ground source system
This is used when there is not enough space to install trenches.
It uses deep drilled boreholes, which require drilling to depths of about 100 metres deep.
Borehole drilling costs: An overview
Estimates vary, but drilling boreholes typically costs between £25 to £40 per metre in depth.
The guideline for a borehole contributing 4kW to the heat system with a standard compressor is roughly 100 meters at £4,000 – £6,000.
And you will need three of these for a 12kW system, so £12,000 – £18,000 for the drilling of the boreholes.
This can be reduced when using an inverter driven heat pump, such as the NIBE S1155.
Breakdown of borehole drilling costs
Let’s assume we’re talking about a 12kW vertical GSHP, designed for a typical-sized single residential property.
Firstly, a specialist contractor using the correct and specialist equipment is needed.
Then, the drilling of boreholes costs about £25 – £40 per square metre depth. The pipe will need grouting and the equipment will need to be mobilised.
The guideline for a borehole contributing 4kW to the heat system is roughly £4,000 – £6,000 and you will need three of these for a 12kW system, so £12,000 – £18,000 for the drilling of the boreholes.
Remember, these are just estimates. The cost of drilling a borehole also depends on:
- The type of equipment
- The site
- The design
- The construction method
- The underlying geology and hydrology.
The cost of installing a vertical GSHP
If we take the 12kW ground source heat pump, the total cost of installation can be around £25,000 – £30,000.
A study by the Department of Energy and Climate Change found that installation costs comprise of 49% equipment and 51% non-equipment.
Of the non-equipment costs, 60% is for drilling boreholes. This is quite a chunk of the total installation cost.
On the other hand, a 12kW horizontal system costs approximately £15,000 – £18,000.
Other cost factors
And the most expensive part of the ground source heat pump installation process is often getting the pipework underground. However, there are other factors to consider.
The size of your heat pump also impacts its cost. This is due to the heat pump unit and components being larger and because of the amount of excavation required.
The cost also depends on the site and the complexity of the installation.
Government support
There are several different government funding options for heat pumps.
After installation is complete, you can apply for the Renewable Heat Incentive (RHI). This is a government scheme to encourage renewable heating.
You can receive quarterly payments for the amount of clean and green heat your system produces.
Trenches
Horizontal ground source heat pumps use trenches, which can be dug by standard plant machinery.
You can expect to pay a contractor £2 – £5 per square metre of digging for a horizontal ground loop.
The issue with horizontal GSHPs is that they use a lot of space and may not be feasible for properties without a large enough garden (usually around 700 square meters).
Furthermore, the possibility of installing a horizontal GSHP depends on the local geology.
Even at 1.2 metres deep, the typical trench depth, the temperature can vary throughout the year and this can make a difference to the effectiveness and efficiency of heating.
Your installer should be able to advise you on whether a horizontal GSHP is right for your property.
Summary
Whether boreholes or trenches are the best option for your ground source heat pump depends on your:
- Property & its surrounding available space
- Budget
- Head demands
- Local geology.
A qualified expert will be able to advise on the most appropriate solution, and this is where IMS Heat Pumps can help.
Drilling boreholes is a fairly expensive job, but it does still provide a good return on investment in the long-term.
Whichever type of ground source heat pump you choose, it will provide a great source of renewable heat and the RHI scheme alongside utility bill savings will create brilliant return on investment.
For some, vertical GSHPs may be the only option due to limited space. For others, a horizontal GSHP is perfect.
Furthermore, an air source heat pump (ASHP) is a solution which is very popular in the UK.
For more information, request a quote today!