Insider Tips with Cooperative Energy Expert Tim Johnson features advice on energy efficiency, new technology and electric appliances. Have a question for Tim? Leave a comment on this post with an email address and he’ll reply.
How a heat pump water heater works:
There are two types of heat pump water heater. The add-on unit is installed on an existing electric resistance water heater. The other, an integrated or drop-in unit, replaces an existing electric water heater. The heat pumps work in essentially the same way, though the add-on units aren’t efficient enough to qualify for an ENERGY STAR rating.
The heat pump draws heat from the surrounding air and uses it to heat water in a tank, like a reverse refrigeration system. Heat pump water heaters have at least one backup electric resistance element in the tank, for use when the ambient air is too cold for heat pump operation or larger amounts of hot water are needed. The cool exhaust air is released into the area where the heat pump water heater sits, cooling and dehumidifying the surrounding air. The new-generation models on the market cannot duct the exhaust air outside. However, manufacturers plan to remedy the external ducting issue.
The heat pump water heater uses electricity to move heat from one place to another,rather than to generate heat. As a result, the unit uses roughly half the electricity of a conventional electric water heater.
Major Benefits:
Water heating is the second largest energy end use in homes, accounting for between 15% and 25% of residential energy consumption, according to the ENERGY STAR Web site. Heat pump water heaters have an energy factor (EF)—a measure of efficiency—of 2.0 or higher, more than double that of an electric resistance water heater, which has an average EF of 0.90. An ENERGY STAR qualified heat pump water heater with an EF of 2.0 has the potential to save 2,662 kWh annually.
DOE has estimated that a heat pump water heater costs $243 annually to run, compared with $539 for a conventional electric water heater.
- Cooling and dehumidifying made easy. Heat pump water heaters are most efficient in warm and damp climates where the unit is able to draw its energy mainly from the surrounding ambient air. In such a climate, the unit also can cool anddehumidify the area it’s in, by releasing the unit’s exhaust air indoors.
Drawbacks:
- Price. A heat pump water heater generally costs more than twice as much as an electric resistance water heater. Excluding installation and any financial incentives, the retail price of an integrated unit is around $1,500. Depending on the retail cost of electricity and the installed cost of the heat pump water heater, including any financial incentives, the payback period is as little as three years. In areas with low electricity rates and limited financial incentives, however, the payback period will be longer.
- Installation. A heat pump water heater can generally be installed in a conditioned or unconditioned space. However, the space must be at least 10 feet square to ensureadequate air exchange for the heat pump. An open basement, a utility area or—in some climates—a garage is appropriate. Professional installation also is important. Make sure the contractor you hire understands all installation requirements.
- Noise. A conventional electric water heater operates almost noiselessly. Most heat pump water heaters, however, operate at between 60 and 70 decibels, about the same level as a window air conditioner. Consider the when deciding where to install a heat pump water heater.
- Use in Northern climates. Because the heat pump draws energy from the surrounding air, heat pump water heaters installed in locations where the ambient air dips below a given level will experience reduced efficiency. This may be an issue for a heat pump water heater installed in a garage. For example, if the heat pump is designed to work at ambient air temperatures of 45° F or higher, the water heater’s electric element will operate whenever the air temperature drops below that level, reducing energy savings.
What’s ahead
If you’re in the market for a new water heater, a heat pump unit may be right for you, especially if it will be used for its dehumidifying capabilities, like in a damp basement.
These are early days for the new-generation heat pump water heaters, and the technology is evolving. Testing of the product will provide valuable information on its performance. As manufacturers receive feedback, changes, large and small, may be made to their models.
