Running tap water

Everything To Know About Water to Water Heat Pumps

Jane Marsh - November 6, 2023

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With climate change being a pressing issue, people worldwide are trying to decrease their carbon footprint and live more sustainable lives. One solution that helps to promote an eco-friendly lifestyle is heating pumps.

While its name might suggest otherwise, heat pumps can cool and warm certain aspects of a home. One type of pump that is very efficient but often less talked about than the air-to-water pump is the water-to-water pump. Learn more about water-to-water heat systems and why they are essential to decarbonizing homes.

What Is a Water-To-Water Heat Pump?

To understand what a water-to-water heat pump is, it is important to know the general function of a heat pump. A heat pump is a system that transfers temperature from one source to another. With conventional heating methods, fuel is burned to generate heat.

However, with a heat pump, it is not generated but only moved from one area to another. In other words, it uses an external source to move heat from a low-temperature source to a high one. A water-to-water heat pump is a system that uses water as its input for both warming and cooling applications.

This type of heat pump can use various water sources such as groundwater, chilled water, seawater and even rivers. When used to warm applications, they extract heat from the source and move it to the desired location.

There are three main types of heat pumps, namely water, air and geothermal. All three work on the same principle but utilize different input sources — ground, water and air.

How Does A Water-To-Water Heat Pump Work?

With this heat pump, there are two different types. The first is an open-loop system that does not rely on antifreeze fluid, which means precautions are needed to avoid freezing. This system utilizes boreholes, moving water from one to another — one cold and one warm.

The heat energy is extracted from the water of one of the boreholes and then the liquid is transferred to the other. With an open loop system significant quantities of water are transferred, which increases overall efficiency.

The other type is a closed-loop system. This system is primarily used in lakes. Where an open system water-to-water heat pump relies on boreholes, this one utilizes pipes to extract heat.

However, the pipes are sealed and absorb the heat when the water is circulated through them. Another major difference is that this one uses antifreeze to prevent the water from freezing in colder temperatures.

Both systems work similarly and utilize the same three main components — evaporator, compressor and condenser. The evaporator is used to extract the heat from the water. To complete this task, a refrigerant is added.

The refrigerant is a liquid used to absorb the temperature from the water. It changes its state between high-pressure liquid and low-pressure gas, releasing the heat it has captured.

When the refrigerant evaporates, the compressor is used to compress the vapor. This increases the pressure and temperature of the chemical. After which, it is sent to the condenser to transfer the heat it has captured.

This is where the heat is moved to the second water source, which is then utilized for warming applications — to cool applications, the process starts at the condensation step and ends at the evaporation stage. When the heat is released, its overall temperature cools and the refrigerant changes from gas to liquid again.

What Benefits Does It Provide?

One major benefit of water-to-water heat pump systems is they allow the use of renewable energy sources. A heat pump still produces some greenhouse emissions(GHG) because it requires electricity to operate. However, the GHG it does release is significantly less than traditional heating systems. These systems are often utilized to decrease the overall emissions a building generates.

What makes this heat pump a great choice is they are very flexible. This water source heat pump can be used for heating and cooling functions. They can warm the water of a home and also increase the temperature.

Water-to-water heat pumps have a high energy efficiency even when compared to other heat pumps. This higher energy efficiency allows for a decrease in power consumption. Due to them using less power, they decrease the cost of energy bills for a home.

Water-To-Water Heat Pump VS Air-To-Water

While both of these heat pumps work and follow the same set of principles, they do have some differences between them. The main and most obvious difference is that they use other sources to transfer heat — water and air. One advantage of an air heat pump system is that it can provide air conditioning capabilities to the home.

This is not the case with a water system, while they can cool certain applications, they can not function as an air conditioner. Water-to-water heat pumps are typically more expensive and complicated to install than air-based pumps. However, both the water and air heat pumps tend to have the same operational costs.

It is worth mentioning that some water systems have higher running and maintenance costs than other water heat pumps. For example, the water open-loop system usually has higher maintenance and running costs than the closed-loop option.

A significant advantage the water system has over the air one is they tend to have a higher coefficient of performance (COP) — the calculation used to calculate the energy efficiency of heat pumps. The higher the value is, the less power the system will use.

This makes them slightly more eco-friendly than air-based heat pumps, which means they can also decrease the cost of electricity bills a little more than their competition. However, this can depend on the type of water source used. Air systems are also more hindered by colder weather conditions than water ones.

Which System Is Right For Your Home?

The answer to this question depends on the homeowner and the house itself. If the home is in colder areas, installing a water-based system might make more sense. Water-to-water heat pumps are compatible with hydronic HVAC systems, whereas air-based devices work with forced-air HVAC systems.

It is also important to consider whether air conditioning is essential for the home. Water-to-water heat pumps do not possess AC capabilities. Both systems have advantages and it is important to weigh them according to the homeowner’s needs.

Water-To-Water Heat Pumps Provide Homes With Clean Energy Solutions

These water heat pumps are a vital tool to allow houses to produce less carbon emissions. While these systems can be expensive to install, they are well worth the investment when looking at their advantages.

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About the author

Jane Marsh

Starting from an early age, Jane Marsh loved all animals and became a budding environmentalist. Now, Jane works as the Editor-in-Chief of where she covers topics related to climate policy, renewable energy, the food industry, and more.