“Mini-split” air-source heat pumps are establishing a strong foothold in northern states, based on the advancing capability of heat pump technology.

JLC visited a jobsite in Maine in April to see technicians from Portland-based ReVision Energy install a system in an existing home, where the unit will “unload” the home’s existing oil boiler during much of the year, limiting the boiler’s heating role to the coldest part of the season when the heating demand is greatest (which is also the period when the boiler will operate at its highest efficiency). During swing seasons, the heat pump will take over much of the home’s heating requirement — an effective use of the heat pump, which operates most efficiently when its outdoor-air heat source is relatively warm.

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