Heat Pumps - Energy from Outside to In

A horizontal closed loop heat exchanger comprises a ‘slinky’ that runs in a ground trench.

A horizontal closed loop heat exchanger
comprises a ‘slinky’ that runs in a
ground trench

Heat pumps gather solar energy absorbed by the ground or air around your home and move it inside to where it’s needed. This energy is then used to heat your property, and in some cases your hot water too.

Ground source heat pumps draw energy from pipes buried in trenches or deep boreholes. This means they are more cost effective when installed in new buildings, when other ground works (like foundations) are ongoing.

Air source heat pumps use an above-ground heat exchanger. This looks like a very large car radiator in a box about the size of a fridge, and needs to be placed near an external wall of your house. Although cheaper and simpler to install, they are less efficient than ground source systems in very cold weather. UK government grants are not available for air source systems.

Key factors in choosing Heat Pumps

There are a few things that you should consider with relation to heat pumps:

  • Heat pumps are powered by electricity. This can be expensive when used on a peak tariff during the day
  • A hot water store enables the heat pump to utilise cheaper night-time tariffs – but this increases installation costs
  • Heat pumps operate at lower temperatures than normal heating systems (around 45-55°C). This makes them better suited to underfloor heating than standard radiators.
  • Ground-source heat pumps are more efficient than air-source, though they are more expensive to install.
  • Don’t underestimate the external ground work needed for the heat exchangers. Typically, a 50m-long trench to a depth of around 1.5 m is needed. Otherwise, a number of boreholes up to 100m deep will need to be drilled in your garden.
  • Whats your budget? An air source heat pump can cost from £3,000-£5,000. A ground source pump costs £6,000-£12,000.

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