ASHRAE OR-16-C058

The Impact of a Heat Pump Water Heater on the Energy Consumption of a Single Detached House

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Organization: ASHRAE
Publication Date: 1 January 2016
Status: active
Page Count: 8
scope:

Heat pump water heaters (HPWHs) are one of the most energy efficient water heating options currently available in the Canadian market. These HPWHs operate by using electricity to circulate refrigerant in a loop to move heat from the surrounding room air into the water within the storage tank. Because the Coefficient Of Performance (COP) of a heat pump is much greater than 1.0, i.e. over 100%, the water heater Energy Factor greatly exceeds that of conventional water heaters. HPWHs use the indoor space as source for energy, so during the winter months, it increases the space heating load; and during the summer months, can reduce the space cooling loads. The purpose of our testing was to study the whole house energy impact of operating a HPWH in a typical Canadian house compared to conventional water heating systems. We performed these tests at a twin house test facility located in Ottawa (Canada). The field study focussed on four key questions: (1) Did the operation of the HPWH have any adverse impacts on the basement air temperature? (2) Was the HPWH operating more efficiently than the baseline water heaters? (3) What if any were the impacts on energy consumption during the heating and cooling seasons? and (4) Were there energy cost savings during the Heating and Cooling Seasons? From the results of our work we concluded that:

The Heat Pump Water Heaters used less energy than a conventional resistance water heater or a gas-fired storage water heater.

The space heating energy use was increased and the space cooling energy use was decreased.

There was no detectable change in overall house energy use during the heating season, but a 20% decrease in the overall house energy use during the cooling season was seen.

Using local utility pricing, energy cost savings were seen in both summer (reduction in energy) and winter (transfer of electricity to natural gas fuel). There were no energy cost savings seen in comparison to a natural gas water heater.

The space temperature effects were temporary and did not affect the building structure.

Document History

ASHRAE OR-16-C058
January 1, 2016
The Impact of a Heat Pump Water Heater on the Energy Consumption of a Single Detached House
Heat pump water heaters (HPWHs) are one of the most energy efficient water heating options currently available in the Canadian market. These HPWHs operate by using electricity to circulate...
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