Heat pump water heaters: a brief guide to this dual-purpose appliance

You may be familiar with heat pumps and certainly water heaters, but did you know that heat pump water heaters (HPWHs) exist? These hybrid units can control indoor climate and heat water while helping you save energy at home. Learn more about how a heat pump water heater works, how it can save you money and energy, and whether it's the right choice for your home.

How does a heat pump water heater work?

A heat pump water heater - also known as a hybrid electric water heater - uses cutting-edge technology to provide homeowners with an energy-efficient option that can lower their costs and reduce their carbon footprint. Heat pump water heaters do not generate heat, but use electricity to move heat from one location to another.  

A common explanation of how HPWHs work is to compare them to refrigerators: using the same technology that refrigerators require to operate, heat pump water heaters generate heat in the same way that refrigerators stay cold. However, there is one key difference: heat pump water heaters work in reverse.

Refrigerators are designed to pull heat from inside and release it into the air, while heat pump water heaters take heat from the air and transfer it to a water tank. Inside a heat pump water heater is a compressor that concentrates the accumulated heat and transfers it to a storage tank where water can then be heated.  

What is the difference between a heat pump and a water heater?  

A heat pump water heater (HPWH) is considered efficient because this device combines a heat pump and a water heater.  

A heat pump in itself is used to regulate the climate by transporting heat. Heat pumps can extract heat from cool rooms and use that heat to warm other rooms, making the warm room warmer and the cool room cooler. This process is particularly efficient for regulating temperature in homes.  

While heat pumps use readily available warm air to heat and cool spaces, water heaters draw energy from electricity or gas and use it to heat water.  

A heat pump water heater combines the functions of a heat pump and a water heater. By using only heat pump technology, heat pump water heaters are particularly energy efficient.

What do I need to know about electric water heaters?

Forty percent of homes use traditional electric water heaters for water heating, and electric water heaters are the second largest contributor to home energy bills.  

Most water heaters are powered by electricity - including heat pump water heaters. However, some electric water heaters use more electricity than others and are not very energy efficient.  

Water heaters are the most traditional choice in water heaters. Water heaters have large tanks that can hold between 20 and 80 gallons of hot water and are constantly filled. When hot water is consumed and removed from the tank, it is immediately replaced with cold water that is heated.  

Because hot water tanks are constantly filled and heated to maintain the water temperature - a process powered by natural gas, fuel oil, propane or electricity - these hot water tanks waste enormous amounts of energy. Water heaters fueled by gas or oil can also lose energy repeatedly when they are vented.  

This repeated waste of excess energy is called standby heat loss. Although storage water heaters are less expensive to purchase, they can make operating costs, utility bills and electricity bills more expensive in the long run.

A typical storage water heater has a life span of 10 to 15 years.  

Tank insulation, forced-air gas water heaters, and sealed combustion water heaters can help reduce energy losses and save on energy costs.  

Why are heat pump water heaters energy efficient?

Water heating accounts for 13% of residential energy use in the United States, and is the second largest consumer of energy in the home. Installing a heat pump water heater is an important project to reduce energy consumption in a home.

Heat pump water heaters do not produce heat directly. Instead, they extract heat from the air that is already there. This process alone makes heat pump water heaters about three times more energy efficient than a conventional electric water heater, depending on the type.

In addition, heat pump water heaters use only one-third to one-half the energy that conventional electric or gas heaters require.  

This energy savings makes them 300-400% more efficient than their gas or electric heating counterparts, which generate heat through carbon-based means such as combustion.  

Not only do heat pump systems require less energy to provide the same output, but they also release no emissions and help reduce the air and climate pollution that comes from a traditional hot water heating system.

Heat pump water heaters can also act as a form of clean energy storage that can help meet the needs of the electric grid during peak demand periods.  

As heat batteries, electric heat pump water heaters can store solar energy generated during the day, reducing the need for electricity at night when electricity demand is greater but less abundant.  

Heat pump water heaters equipped with electric resistance heating (hybrid heat pump water heaters) can be programmed to switch from standard operation to electric operation when hot water demand is high.  

Some heat pump water heaters offer several settings, including high-efficiency and economy modes that use only the heat pump to heat the water, as well as a vacation or timed mode that can be set to sleep until the next need.

Overall, heat pump water heaters provide homeowners with clean, energy-efficient heating and cooling options that prevent pollution and produce zero emissions.