How Does a Heat Pump Water Heater Work?

Fast read

Heat pump water heaters are a more efficient option than regular water heaters. They use electricity to move heat instead of creating it. Here's a quick overview of how they work:

  1. Heat Extraction: The HPWH extracts heat from the surrounding air using an evaporator coil filled with refrigerant.
  2. Heat Transfer: The refrigerant absorbs this heat and evaporates. It then passes through a compressor, increasing its temperature and pressure.
  3. Water Heating: The hot refrigerant travels through a condenser coil around the water storage tank, transferring its heat to the water.
  4. Cycle Repeat: The refrigerant cools, returns to liquid form, and the cycle restarts.

HPWHs are typically installed in areas with ample airflow and moderate temperatures. Tankless water heaters use less energy than traditional water heaters, which saves money over time. This is because they consume less energy. Proper installation and maintenance are key to maximizing their efficiency and lifespan.

How Does a Heat Pump Water Heater Work?

If you’re a homeowner interested in energy-efficient water heating solutions, you’ve likely come across heat pump water heaters (HPWH). These systems offer an innovative way to heat water, utilising technology that can significantly reduce energy consumption compared to traditional methods. But how do these water heaters work? Let’s dive into the mechanics and benefits of this advanced system.

Understanding Heat Pump Technology

Most homeowners are familiar with heat pumps used for heating and cooling their homes. These water heaters operate on a similar principle, but instead of regulating your home’s temperature, they heat your water. The main process involves transferring heat instead of making it, which helps make them extremely efficient.

The Basic Mechanism

A heat pump water heater uses electricity to transfer heat from one place to another. This process is akin to how a refrigerator works but in reverse. A fridge removes heat from the inside and releases it outside. A heat pump water heater extracts heat from the air and transfers it to the water tank.

Components and Operation

Here’s a step-by-step breakdown of how these water heaters function:

  1. Evaporator Coil: The system has an evaporator coil filled with refrigerant. Air from the surrounding space is drawn over the evaporator coil.
  2. Heat Absorption: As the air passes over the coil, the refrigerant inside absorbs heat from the air, causing it to evaporate.
  3. Compressor: The now gaseous refrigerant passes through a compressor, which increases its temperature and pressure.
  4. Heat Exchange: The hot, compressed refrigerant travels through a condenser coil wrapped around the water tank. Here, it transfers its heat to the water.
  5. Release: After releasing its heat, the refrigerant returns to its liquid state and cycles back to the evaporator to start the process again.

Installation Requirements

For optimal performance, heat pump water heaters should be installed in locations that remain within the 4.4º–32.2ºC range year-round and provide at least 28.3 cubic meters of air space. Common installation sites include basements, garages, or utility rooms with sufficient airflow.

High Efficiency and Energy Savings

Heat pump water heaters are more efficient than electric resistance water heaters because they move heat instead of creating it. This means they use less energy to heat water. These heaters are a better choice for saving energy and reducing energy bills. This efficiency translates into substantial energy savings for homeowners, making HPWHs an attractive investment despite their higher upfront costs.

Combination Systems

In addition to stand-alone models, some heat pump systems integrate water heating with space heating and cooling. These combination systems extract heat from the air inside your home in the summer and from the outside air in the winter. By consolidating these functions, you can achieve comprehensive energy savings and a more streamlined home heating solution.

Geothermal Heat Pumps and Desuperheaters

For those utilising geothermal heat pumps for home heating and cooling, a desuperheater can be added to the system to assist with water heating. A desuperheater is a small heat exchanger that uses hot gases from the heat pump to heat water. This setup can be particularly efficient during summer months when excess heat from the home can be diverted to water heating.

heat pump water heater ground source geothermal

Selecting the Right System

When choosing a water heater, consider the following factors:

  • Size and First-Hour Rating: Ensure the system meets your household’s heat pump hot water demands.
  • Fuel Type and Availability: Verify that electricity is a viable option for your home.
  • Energy Efficiency: Look for systems with high energy factors (EF) for better performance.
  • Overall Costs: Factor in both the initial investment and potential long-term savings.

Installation and Maintenance

Proper installation is crucial for the efficient operation of a heat pump water heater. Hiring a qualified professional is recommended to ensure compliance with local building codes and optimal system performance. Regularly cleaning the air filter and checking for leaks can make your HPWH last longer and work better.

Additional Energy-Saving Tips from Heat Pump Hot Waters

After installing your heat pump water heater, you can save more on water heating running costs by using extra energy-saving methods.

  • Insulate Hot Water Pipes: Reducing heat loss in your plumbing system can help maintain water temperature and reduce energy use.
  • Lower the Thermostat: Setting your water heater to a lower temperature (120ºF is often sufficient) can save energy.
  • Use Water-Saving Fixtures: Installing low-flow showerheads and faucets reduces hot water consumption.


Heat pump water heaters represent a significant advancement in home water heating technology, offering substantial energy savings and environmental benefits. By understanding how these water heaters work, you can make an informed decision about whether this system is right for your home.

To have efficient and reliable hot water for many years, choose, install, and maintain a water heater properly. This will ensure that your hot water system works effectively. Proper installation and maintenance are key to the longevity of your hot water system.

Choose a water heater such as Reclaim that meets your needs and budget. Make sure to follow manufacturer instructions for installation and maintenance. Regular maintenance will keep your hot water system running smoothly.

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