Water Source Heat Pump

What are Water Source Heat Pumps and how much they can save you?

What is a Water Source Heat Pump?

Water Source Heat Pumps use the energy stored in a water source to heat your home and provide hot water all year round. Pipes are submerged in a river, stream or lake where temperatures remain at a relatively constant level of between 7-12c.

Water Source Heat Pumps can be installed as either an open or closed loop system. An open loop system uses ground water from a lake or well. In an open loop system water is extracted and fed directly into the heat pump where the energy raised through compression is extracted as heat. This increased heat is transferred by the heat exchanger to your property’s heating/hot water system where it is readily available for use. In this type of installation you may need environment agency consent to extract and discharge water from these sources, however Ecovision can advise and manage this application for you when required.

A closed loop system uses a refrigerant in a closed loop to transfer energy/heat from the water source, e.g. a lake. Pipes are laid in the lake in which a liquid refrigerant absorbs the waters heat and transfers this heat to a heat pump located inside the house.

Water Source Heat Pump Efficiency

Virtually maintenance free and silent to run, a Water Source Heat Pump is able to produce more energy than they consume, with every 1kW used providing up to 4kW of energy out.

The efficiency of a Water Source Heat Pump is referred to as the Coefficient of Performance or CoP. This is the ratio between heat delivered and power consumed which will vary throughout the year depending on the outside temperature.  The average UK winter heating temperature has an average CoP of 3.4:1, providing 3.4 units of heat for each unit of energy consumed, resulting in significant energy savings. 

How Does a Water Source Heat Pump Work?

A Water Source Heat Pump will provide an efficient modern energy solution to heating your property. Traditional, fossil fuel boiler systems work by producing on-off bursts of heat to maintain the desired room temperature. Water Source Heat pumps work much more efficiently by supplying hot water to the radiators at a lower but constant temperature, giving you a controlled level of warmth and hot water.

A Water Source Heat Pump is based on one simple principle, heat transfer – using a small amount of energy to transfer low-grade heat from the air to high-grade heat, heating water to high temperatures. Essentially transferring heat from a ‘free heat source’ like the air to a ‘heat sink’ like your home.

This is a similar operation to a refrigerator – but in reverse and is a process known as the vapour compression cycle.


1. The refrigerant inside the coils begins as a cold low pressure liquid.

2. As the refrigerant passes into the evaporator, warm air from the outside passes over the evaporator. This causes the refrigerant to increase in temperature, due to its low boiling temperature, and change to a hot gas.

3. This hot refrigerant gas then enters the compressor where its temperature increases further as a result of the compression process – much like a bicycle pump heats up during its use.

4. The hot refrigerant gas is then condensed as it passes across one side of a plate heat exchanger, at which point, the heat is transferred to the cooler side (water side) of the heat exchanger. This, now high temperature water, is distributed via the buildings heating circuit.

5. As the temperature of the refrigerant decreases its state changes from a gas back to a cool liquid.

6. Despite dropping in temperature, the cool liquid still has a high pressure which must be reduced. To reduce this pressure the liquid refrigerant passes through an expansion valve causing the pressure to drop and the temperature to lower further. This process returns the refrigerant to its initial state of cool low pressure liquid.

7. This process is repeated to provide a constant temperature to the property.

In summary, as the high temperature gasses pass the heat exchanger, the heat is transferred to create hot water capable of heating the property as well as providing hot water.

Frequently Asked Questions

Water Source Heat Pumps can reduce your annual heating and hot water bills  against fossil fuel alternatives and often pay for themselves within the grant period set out within the Renewable Heat Incentive (7 years of payments for a domestic property).

However, each and every property is different so upfront cost, bill reduction and your ROI is never going to be a one answer fits all. The best way to find out how much a Water Source Heat Pump can reduce your heating and hot water bills is to speak to us directly for a free no obligation quote

What is the Renewable Heat Incentive?

The RHI is a Government backed scheme which pays the owner of a renewable technology, such as a heat pump, for generating renewable energy on site. To qualify for these quarterly payments, which last seven years, you will need to use an MCS accredited company – such as Ecovision – and ensure your MCS accredited product is installed to MCS standards.

The MCS (Microgeneration Certification Scheme) is there to ensure the system is safely installed by professionally qualified installers and performs to the standards required by the Government.

Learn more about the Renewable Heat Incentive here…

Can I change the temperature within my home?

The heat pump will be weather compensated which means that you set the temperature you want within your home and the heat pump uses the least amount of electricity required to achieve the desired temperature.

As the outside temperature reduces, or indeed increases, the heat pump will automatically react and adjust its output to maintain your chosen internal temperature. It does this via a range of sensors strategically placed within the system – you simply set your desired temperature and let the heat pump do the rest.

Our customers often report an improvement in comfort levels as the heat pump maintains a constant temperature rather than allowing the internal temperature to fluctuate based upon a traditional time clock.

How do I apply for the Renewable Heat Incentive?

The RHI is administered by Ofgem and as the owner of the system, you will need to make the application for the RHI. We will of course ensure you have all the required paperwork to successfully complete this; this is supplied as part of your handover pack and we will be on hand to help at any point throughout the process.

Learn more about the applying to the Renewable Heat Incentive here…

Or make your RHI application directly here…

How long do Water Source Heat Pumps take to install?

The installation of a Water Source Heat Pump can take anywhere between 4 weeks and 16 weeks, depending on the size and complexity of the pump location. As there are many elements that come together during this process Ecovision offer an all-inclusive installation, including everything from digging the trenches to commissioning the Water Source Heat Pump.

Will a Water Source Heat Pump keep me warm in winter?

Yes, the system will be capable of providing all of your heating and hot water throughout the year without any requirement for a supplementary boiler.

Do I need to coordinate any other trades on site?

No, Ecovision can undertake the entire installation, providing the complete design, supply, installation and commissioning of the system, without any need for third parties or subcontractors.

During Ecovision’s many years of business we have found the biggest issue for customers is ensuring that everyone knows what and when their responsibility starts and ends. We have found that by offering the complete installation we ensure that we remain in control of the whole process as well as being entirely responsible for the successful completion of the installation with our in-house installers reporting directly to Ecovision.

Does a Water Source Heat Pump require lots of maintenance?

Generally Water Source Heat Pumps require very little maintenance, as they are a sealed unit, much like your fridge. Though it is recommended that you inspect and clean your Water Source Heat Pump annually, clearing any build-up of leaves or debris from behind the unit.

Ecovision can complete this task as part of an annual service, leaving you with absolutely no maintenance requirements.

Will a Water Source Heat Pump work with my existing radiators?

Ecovision will have to complete a full room-by-room emitter (radiator) assessment before any installation takes place to ensure your existing radiator circuit is capable of emitting the heat required. This a government requirement in order to be eligible for the RHI subsidy.

We usually find that most of the radiators are suitable but that some will need to be changed to meet the government’s accreditation standards. These changes will ensure the lowest possible running costs and the cost of any changes will be made clear in your quotation