Optimal Heat Pump Water Heater: Energy‑Efficient Hot Water Solutions

How Heat Pump Work

Heat pump water heaters use electricity to transfer heat from one place to another, rather than producing heat directly. Therefore, they can be two to three times more energy efficient than conventional electric resistance water heaters. To dissipate heat, heat pumps act in the opposite way as refrigerators.

While the refrigerator takes heat from inside the box and dumps it into the surrounding room, a standalone heat pump air water heater takes heat from the surrounding air and dumps it - at a higher temperature - into a tank to warm the water. It is possible to purchase a standalone water heating system with a heat pump as an integrated unit with a built-in water tank and backup heating elements. You can also retrofit a heat pump to work with an existing conventional storage water heater.

Heat pump water heaters require installation in locations that remain in the range of 40º - 90ºF (4.4–32.2ºC) all year round and provide at least 1,000 cubic feet (28.3 cubic meters) of air space around the water heater. The cool exhaust air can be discharged indoors or outdoors. Install them in a place with excessive heat, such as a room with a stove. Heat pump water heaters will not work efficiently in cold rooms. They tend to cool the rooms in which they are located. You can also install an air source heat pump system that combines heating, cooling and hot water. These combined systems extract heat into the interior from the outside air in winter and from the inside air in summer. As they remove heat from the air, any type of air source heat pump system works more efficiently in warm climates.

Homeowners mainly install geothermal heat pumps - which extract heat from the ground in winter and from indoor air in summer for heating and cooling their homes. A cooler can be added to the geothermal heat pump system to heat the water. A desuperheater is a small auxiliary heat exchanger that uses superheated gases from the heat pump compressor to heat water. This hot water then circulates through a pipe to the domestic hot water tank.

Heat pump domestic hot water heaters are also available in tankless or on request versions. In summer, the cooler uses excess heat that would otherwise be thrown into the ground. Therefore, when the geothermal heat pump is often operated in summer, it can heat all your water.

In fall, winter and spring - when the cooler does not produce as much excess heat - you will have to rely more on its storage or request a water heater to heat the water. Some manufacturers also offer three-way geothermal heat pump systems that provide heating, cooling and hot water. They use a separate heat exchanger for meet all of a household's hot water needs.

 

Selection of a Heat Pump Water Heater

Heat pump water heater systems typically have a higher upfront cost than conventional water heaters. However, they have lower operating costs which may be offset by their higher purchase and installation prices.

Before purchasing a heat pump water heating system, also consider the following:

• Size and grade for the first hour
• Fuel type and availability
• Energy efficiency (energy factor)
• General costs

If you are considering installing an integrated water heating, space heating and heat pump cooling system in your home, see also our information on air source heat pumps and geothermal heat pumps.

 

Installation and Maintenance

Proper installation and maintenance of a heat pump water heating system can optimize its energy efficiency.

Proper installation depends on many factors. These factors include fuel type, climate, local building codes, and safety issues. Therefore, it is best to have the heat pump installed by a qualified plumbing installer (or geothermal heat pump installer / designer).

When choosing a qualified specialist, do the following:

• Ask for a quote in writing
• Ask for references
• Check the company at your local Better Business Bureau
• Check that the company obtains a local permit if necessary and that it understands local building codes.

Periodic maintenance of the water heater can significantly extend the life of the water heater and minimize the loss of efficiency. Read the owner's manual for detailed maintenance recommendations.

 

Improving Energy Efficiency

Once your water heater is properly installed and maintained, try additional energy saving strategies to lower your water heating bills. Some energy-saving devices and systems are more cost-effective to install with the water heater.