Heat Pumps Water Heater Systems

Until recently, heat pumps were merely heating and cooling devices. Now, besides those traditional uses, heat humps may also provide water heating.

Heat Humps Water Heaters performance

Heat pumps water heaters consume electricity, as traditional systems, but they are on average three times more efficient than common systems, expressed by their COP (Coeficient Of Perfomance), and also by ratings like SEER and HSPF.

Stand-alone Air Source Heat Pump Water Heaters

Heat pump water heater systems can be…

- stand-alone systems or
- integrated water-heating-space-conditioning systems.

Basically, a stand-alone heat pump water heater is a refrigerator working in reverse: it pulls heat from the surrounding air, increases its temperature and damps it into a tank to heat the water.

Integrated water-heating-space-conditioning systems

You can install an heat pump that provides both heating, cooling, and water heating. Such system may involve geothermal heat pumps or air source heat pumps.  In the second case, since the system drives heat from the outdoor air (in the winter) or from the indoor air (in the summer) climate is an important element: air source water heater pumps work better in a warm climate.

Ground heat pumps and water heating
 

Ground heat pumps can be used to water heating (besides air conditioning). For water heating, you should add a small, auxiliary heat exchanger (called a desuperheater) to the geothermal heat pump. Desuperheaters use superheated gases from the heat pump's compressor, and pipe it to a storage water heater tank.

The system is particularly efficient in hot and moderate weather, when the desuperheater can use the excess heat produced by the heat pump to heat the water.

The triple-function geothermal/ground heat pump systems - providing heating, cooling, and hot water – are becoming increasingly common.

Cost

The cost of a stand alone heat pump water systems may range $from 600 to over $2000 (more $300 to $700 to install).
 

Requirements and drawbacks

Heat pump water heaters do not operate efficiently in cold climates and cold spaces. Besides, they cool the spaces they are in, which may also be a disadvantage, namely in cold climates.

Air source heat pump water heaters require climates or locations offering adequate temperatures: 40º/90ºF (4º/32ºC) year-round. They also require adequate air space (at least 1,000 cubic feet: 28 cubic meters) around the water heater.

Warranty

Warranties are very variable: they may range from 1 year to 7 years and vary by parts and manufacturers.

Costs and Payback

Conventional water heaters demand a lower initial investment, but heat pump water heaters offer lower operating costs (typically a third). The estimated recovery of the initial investment ranges from 2 to 5 years, but it depends very much on electricity prices.