Summary: Commercial heat pumps can produce domestic hot water using about a third of the energy of conventional gas and electric boilers. Heat pump water heaters (HPWHs) using CO2 refrigerant can even deliver hot water well below freezing temperatures. Heat pumps extract heat from the air (even cold air) and transfer that heat into the incoming cold water. Seattle requires heat pump water heating for most new buildings and new “central water heating” equipment in existing hotel and multifamily buildings. Central water heating refers to water heating systems that serve multiple dwelling or sleeping units, a circulating hot water system, or a hot water system that serves numerous building areas.

Date Revised: 11/10/2021

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