Heat Pump Water Heaters: Your Energy-Efficient Alternative
Heat pumps are most often thought of as heating and cooling systems, but they can also be used to heat water—either as stand-alone water heating systems, or as combination water heating and space conditioning systems. Heat pump water heaters typically have a higher purchase price than conventional units, but their lower operating costs can provide a good return on your investment.
How they work
Heat pump water heaters use electricity to move heat from one place to another instead of generating heat directly. Therefore, they can be two to three times more energy efficient than conventional water heaters. To move the heat, heat pumps work like a refrigerator in reverse. While a refrigerator pulls heat from inside the box and into the surrounding room, a heat pump water heater takes heat from the surrounding air and dumps it (at a higher temperature) into a tank to heat water.
You can purchase a stand-alone heat pump water heating system as an integrated unit with built-in water storage tank and backup resistance heating elements, or you can install a system that combines heating, cooling and water heating. These combination systems pull their heat indoors from the outdoor air in the winter and from the indoor air in the summer. Because they remove heat from the air, any type of air-source heat pump system works more efficiently in a warm climate.
Energy efficiency and cost
The efficiency of a water heater is measured by energy factor (EF), which indicates the amount of hot water produced compared to the amount of power or fuel consumed. The higher the energy factor the more efficient the water heater. Heat pump water heaters have a much higher energy factor than conventional units; a typical heat pump unit has an EF of 2.0, compared to 0.65 for a high-efficiency natural gas storage system.
It's important to remember that a higher energy factor doesn't always result in lower operating costs. If you are considering a heat pump water heater, take into account the size of the unit, your water heating needs and energy prices.
If you choose to install a heat pump water heater, purchase a unit that is ENERGY STAR® qualified for high-efficiency performance. ENERGY STAR units can save the average household up to $300 in annual energy costs, according to the U.S. Environmental Protection Agency.