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Water Source Heat Pump
A water source heat pump is a renewable type of central heating system. It collects heat from an outdoor water source and lets us use it for heating our homes.
You may have heard of an air source heat pump, or even a ground source heat pump. Water source heat pumps (WSHP) are a less well known, but equally innovative type of central heating.
This guide will explain how they work and help you decide whether a WSHP is right for your home.
What is a water source heat pump?
A water source heat pump is a type of central heating system. It warms the radiators in our homes using heat from an outdoor water source, such as a lake, river or pond. When combined with a hot water cylinder, a WSHP can also provide hot water.
How does a water source heat pump work?
Put simply, a water air source heat pump extracts warmth from a body of water, such as a lake, pond or river. It uses electricity to boost this heat to a level that covers our central heating needs.
There are two different types of WSHP: open loop and closed loop systems. Both involve submerging pipes in water to collect heat energy, but there are important differences. We’ll explain these below.
Open and closed loop systems
In a closed loop system, the water from the pond, lake etc. doesn’t enter any of the pipework. Instead, the sealed pipes are filled with an antifreeze solution. This collects heat from the water outside the pipes without coming into contact with the water itself. The pipes then deliver this heat energy to the heat pump unit.
Closed loop systems usually suit lakes or ponds.
Open loop systems extract the water itself from its source and send it to the heat pump unit. This requires drilling a borehole. Pipes from the bore hole move the water to the heat pump unit, where it transfers its heat to the water in your central heating system. The colder water returns to the water source via a second bore hole.
Open loop systems are usually used near rivers, to extract heat from aquifers, or even mine water.
Pros and cons of a water source heat pump
- Very efficient
- Low carbon
- Could save you money on your heating bills, depending on your current system
- Very site specific – you’ll need access to a suitable water source
- You’ll probably need to upgrade your radiators
- Less efficient in poorly insulated homes
Is a water source heat pump right for my home?
As with all heat pumps, you’ll get the most out of a WSHP if:
- You have a well-insulated home
- You upgrade to (or already have) radiators with a large surface area
For more information on these points, check out our general heat pump guidance.
If you want your heat pump to provide hot water as well as heating, then you’ll need a hot water cylinder. Its size would be determined by your home’s hot water needs, as well as the space you have available for the cylinder itself. If space is an issue, you could potentially choose a heat battery instead of a hot water cylinder.
With WSHP, you’ll also have to consider the following:
Closed loop system considerations
Most closed loop systems use a pond mat collector. The pond mat floats on the surface of the water, with the pipework on its underside submerged. If you’re using a pond mat collector, then you’ll need to ensure that:
- The water is deep enough. How deep it needs to be depends on how fast-flowing the water is
- You can properly secure the system in place
- There’s no danger from debris or water traffic (e.g. boats)
Open loop system considerations
You’ll need to work closely with the installer to ensure the system is designed properly. This includes:
- Getting the right distance between the bore hole you take (abstract) water from, and the bore hole you return (discharge) it to.
- Making sure the boreholes won’t clog
- Limiting the risk of damage through freezing
With an open loop system, you’ll also need to contact the Scottish Environmental Protection Agency (SEPA) to get:
- Permission to test/drill bore holes
- An abstraction and discharge license (if you’re abstracting more than 20 cubic metres of water per day)
Water source heat pump costs and funding
How much does a water source heat pump cost?
The heat pump unit itself can range from around £6,000 – £11,000. However, the total cost of a WSHP installation can vary considerably, depending on the complexity of the installation process.
Water source heat pump grants and funding
Water source heat pump grants of £7,500 are available through Home Energy Scotland. Householders who live in remote or rural areas of Scotland may be eligible for £9,000 towards a water source heat pump.
For the most up-to-date information about heat pump grants, visit the Home Energy Scotland grant and loan page. Alternatively, you can call Home Energy Scotland free on 0808 808 2282.
Changeworks delivers Home Energy Scotland in the south east and Highlands and Islands on behalf of the Scottish Government and Energy Saving Trust.
As well as providing free, impartial expert advice to thousands of people every month to help them to keep warm in their homes for less, they identify funding opportunities for households seeking to install energy efficiency measures.
For more information, give Home Energy Scotland a call on 0808 808 2282 or email and the team will be happy to help you.