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Project Launch: 01/01/2019

Partner: National Renewable Energy Laboratory (NREL)

NREL’s research partnership with ComEd examined the technical aspects and potential energy savings of high-efficiency variable-speed air-source heat pumps in cold climates.


Recent technological advances in variable-speed compressors and electronically commutated fan speed modulation allow some modern heat pumps to operate efficiently in more extreme temperatures than traditional models.

Through laboratory testing, NREL mapped the expected performance of ducted split heat pump systems under steady-state conditions to determine the coefficient of performance (COP) and unit capacity across a range of modes and conditions. These findings were used to develop performance curves that accurately represent how this technology would perform in the ComEd service territory.

Results and Outcomes

The higher COP of the high-efficiency heat pump under Chicago’s low winter temperatures resulted in significant heating energy savings in all three buildings simulated: single-family home, strip mall and low-rise office building. The higher compressor COP also contributed to moderate annual cooling energy savings. The high-efficiency supply fan motor and variable-speed controls of the high-efficiency heat pump provided additional fan energy savings for all three building models.

The strip mall building shows the highest whole-building energy savings (35%) over its respective baseline. The low-rise office building’s savings are similar (28%), while the single-family home building has a slightly reduced energy savings (22%) due to reduced supply fan energy savings. Overall, all buildings show significant energy savings over their respective baseline and make a strong case for the utilization of cold climate heat pumps in ComEd’s service territory.