Water source heat pumps

A water source heat pump uses the heat energy from water to provide heating and hot water for your home. It extracts energy from the water and turns it into heat, even when the water temperature is lower than the air temperature you need in your house.

There are two main water source heat pump designs:

• closed loop systems
• open loop systems

In both systems, electricity is needed to power the compressor, but the amount of heat energy delivered to your home is more than the amount of electricity used by the system. This means that installing a heat pump could reduce your energy bills and carbon emissions.

Not sure where to start with heat pumps? Visit our heat pump hub.

Closed loop systems are used in lakes, lochs, or large ponds.

In a closed loop system, sealed pipes filled with an anti-freeze fluid are submerged under the water. As this fluid is pumped through the pipes, it gathers heat energy in the water. This fluid is circulated back to the heat pump. 

For more information, read our guide on how heat pumps work.

Open loop systems are used with boreholes near rivers or areas with suitable geological conditions.

Instead of using a fluid to transfer the heat through submerged, sealed pipes, an open loop system takes water from a borehole. It then lifts it to the surface, extracts heat energy and then returns the cooled water to a separate borehole. 

However, as there’s no anti-freeze, there is a potential risk that open loop system pipes could freeze as colder water leaves the heat pump. Therefore, it’s important that the heat pump is correctly sized and there’s enough flow of water to ensure this doesn’t happen. 

Open loop systems move large volumes of water through the heat exchanger (more than might be possible with a closed loop system). As a result, open loop water source heat pumps are often more efficient than equivalent ground or air source heat pumps.

However, they also have higher operation and maintenance costs. You’ll need to factor this in when thinking about your overall running costs. An experienced installer should be able to offer you advice on working with either open or closed loop systems based on your specific site location.

Water source heat pumps can be installed in many types of homes. However, you should consider a few things before deciding if one is right for you.

When it comes to installers, we recommending finding an installer and system that are both accredited through the Microgeneration Certification Scheme (MCS).

• An efficient and low carbon source of heating
• They can heat your home and provide hot water
• Reliable performance throughout the year