Water Source Heat Pumps

What are water source heat pumps?

Water source heat pumps work on a similar principle to both air source and ground source heat pumps. Instead of taking advantage of the heat in the air or the ground, they take advantage of the relatively consistent temperatures found in a body of water.

A series of flexible pipework is submerged in a body of water, like a lake, river or stream. A heat pump pushes working fluid through the network of piping, and this fluid absorbs the heat from the surrounding water as it goes.

This working fluid is then compressed by an electric compressor, in a similar fashion to the other types of heat pump, which raises the temperature. A heat exchanger can then be used to remove the heat entirely from this working fluid, providing you with hot water that can be used for space heating (in radiators or under floor heating). It can even be plumbed into your hot water system, where a boiler can just provide the small amount of additional heat needed to bring it up to the required temperature, so it can be used for showers and baths.

Once the heat has been removed from the working fluid via the heat exchanger, it is once again pumped back through the pipework, thereby completing a continuous cycle.

The benefits of a water source heat pump

The heat transfer rate from water is higher from the ground, making them more effective than ground source heat pumps. In addition if using a water source heat pump with a moving body of water, the heat is constantly being replaced, as new warmer water replaces the cooler water that has had its heat extracted by the working fluid.

For every 1kW of energy required to run a water source heat pump, 4-5kW of equivalent of heat energy is produced that can be used to warm your home, making them more efficient than both air and ground source heat pumps.

The supply of hot water is also pretty much constant, despite being cooler in the winter; the body of water will still possess sufficient heat to enable the water source heat pump to operate in the winter. An issue arises if the body of water completely freezes.

Unlike ground source heat pumps, where bore holes or trenches need to be dug on your plot for the piping, the pipework for a water source heat pump is relatively simple to install; it simply needs to be situated within a body of water, which should have little impact on your plot of land.


    • The installation of a water source heat pump is relatively easy if there is a body of water available on your property.
    • Water source heat pumps have a higher coefficient of performance than the ground source and air source heat pumps, so for every unit of electricity used to operate them, they can produce more hot water.
    • There is little visual impact on the property, since all the pipework in the water source heat pump system is submerged within the body of water.


    • A water source heat pump is reliant on there being a body of water at your property.


    • Anywhere around £10k