Water source heat pumps (WSHPs) have been in use since the late 1940s and transfer warmth from a source of water to a property.

Often associated with commercial developments with a nearby water source, a water source heat pump can deliver impressive results if, for example, it is in a small stream or river with water temperatures between 5-8°C.

What is a water source heat pump (WSHP)?

Unlike an air source heat pump which absorbs heat from the air outside or a ground source heat pump which relies on the temperature increase underground, water source heat pumps utilise the constant temperature of water as an exchange medium.

This means that WSHPs can achieve a high efficiency of between 300-600% on cold winter nights. Air source heat pumps can expect to reach 175-250% in the same conditions.

How does it work?

A water source heat pump system is made up of reverse cycle heat pump units, interconnected by a water loop. Each unit provides specific air comfort requirements in the area that its installed in.

The WSHP transfers heat from the water loop through the unit’s purposely-designed refrigerant-to-water heat exchanger, before moving it into the air.

Units function in heating mode during cold weather conditions, in order to generate the additional heat required to warm up the property, meaning that heat is provided to each individual unit from the water of the loop.

An energy efficient fluid heater will need to be installed in the loop to assist the heating process in cases when there isn’t enough heat in the loop water.

Benefits of a water source heat pump

They are a sustainable and efficient heating solution, generating less CO2 emissions than more traditional systems.

Although electricity is required to power a water source heat pump in order to circulate water through the loop, you can expect to receive between two and four units of heat in return for every unit of electricity used.

Depending on which heating system you replace, it could save you between £395 and £2,000 a year, according to the Energy Saving Trust.

What type of systems are available?

There are three different types of system to choose from. For further information on which type would best suit you, contact your nearest HIES installer for expert advice.

Closed loop

A closed loop system would be the lowest cost option for properties with access to a sufficient source of water.

Starting at the building, a supply line is inserted through the ground to the water, intertwining into circles of a minimum of eight feet beneath the surface in order to prevent freezing. Coils need to be located in a water source meeting the minimum conditions necessary for quality, depth and volume.


A hybrid system uses geothermal resources, sometimes mixed with outdoor air, and is ideal for locations where the cooling requirements exceed the heating needs.

Open loop

An open loop system utilises a well or a surface body water as the heat exchange fluid travels through the heat pump.

After it has dispersed though the whole system, the water returns to the ground via the well, a recharge well or a surface discharge.

However, this type of system is only practical if you have access to a reasonable supply of clean water. All regulations and codes in relation to groundwater discharge must also be completed.

Should you get a water source heat pump for your home?

Before you can decide whether you are going to purchase a water source heat pump you will need to consider its suitability. Very much like air source heat pumps or ground source heat pumps, it may be necessary to install underfloor heating and bigger radiators in order to get the most benefit from a water source heat pump.

There are several other factors to take into consideration:

  • Do you have access to a sufficient water supply?

The more heat that your property needs, the bigger the water source required.  Water source heat pumps really need a lake or river adjacent to your property and permission to use this for your heat pump source. If the water source is not sufficient, then the WSHP will reduce the temperature of the water and the system will not run efficiently. In extreme circumstances, this could even cause the water to freeze.

  • Is your property compatible with a water source heat pump?

Not only must your property be near a sufficient water supply, but you will also need enough space to lay piping from the building to the water.

Internally, you will have to provide space for the system’s compressor. As these make a low humming noise, it’s preferable that these are located where they will cause minimum annoyance.

  • Is your existing heating system compatible with a water source heat pump?

As with other heat pumps, a well-insulated property will benefit most from a WSHP system as the system is designed to maintain a consistent temperature within the property. A HIES installer will be able to give you expert advice on whether it will operate efficiently with your current radiators, etc.

Should you obtain planning permission? 

Water source heat pumps are considered as ‘permitted developments’ by planning authorities in most cases. That means that providing they are within the boundaries of your property, they can be installed without specific planning permission.

However, in some cases restrictions may apply. It is recommended that you check with your local planning department to check if permission is required before starting installation.

Costs and savings

Although a water source heat pump can come with a relatively high initial expense, it’s worth considering the long-term savings that you might benefit from.

What is the cost of a system?

The cost of a water source heat pump can seem expensive, with an estimated cost of around £10,000.

Savings to expect 

Expected savings will largely depend on two main factors – how efficient the heat pump runs, this will depend on location, the water source, etc; and how well insulated the property is. A HIES installer will be able to give you further advice on what savings you could make.

Using a reputable company

A water source heat pump system is a considerable investment, so it is vital that you choose a reputable installer for your project.

All HIES Accredited Installers are continually vetted in many areas in order to give consumers trust, confidence and peace of mind.

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