Air Source Heat Pumps: The Best of Both Worlds

A smarter solution for members seeking a way to heat their homes more efficiently year-round

Air Source Heat Pumps

An air source heat pump (ASHP) can provide efficient heating and cooling for your home. When properly installed, an air source heat pump can deliver one-and-a-half to three times more heat energy to a home than the electrical energy it consumes. This is possible because a heat pump moves heat rather than converting it from a fuel like combustion heating systems do.ASHP graphic

Air source heat pumps have been used for many years in nearly all parts of the United States, but until recently they have not been used in areas that experienced extended periods of subfreezing temperatures. However, in recent years, air source heat pump technology has advanced so that it now offers a legitimate space heating alternative in colder regions.

 

Ductless ASHP

Ductless, mini split system heat pumps make good retrofit add-ons to houses with non-ducted heating systems, such as hydronic (hot water heat), radiant panels, and space heaters (wood, kerosene, pro­pane). They can also be a good choice for room additions where extending or in­stalling distribution ductwork is not fea­sible, and very efficient new homes that require only a small space conditioning system. Be sure to choose an ENERGY STAR® compliant unit and hire an installer familiar with the product and its installation.

Like standard air source heat pumps, mini splits have two main components: an outdoor compressor/condenser and an indoor air handling unit. A conduit, which hous­es the power cable, refrigerant tubing, suction tubing, and a condensate drain, links the outdoor and indoor units.

Selecting a Heat Pump

Every residential heat pump sold in this country has an EnergyGuide label, which displays the heat pump’s heating and cooling efficiency performance rating, comparing it to other available makes and models.

Heating efficiency for air source electric heat pumps is indicated by the heating season performance fac­tor (HSPF), which is the total space heating required during the heating season, expressed in Btu, divided by the total electrical energy consumed by the heat pump system during the same season, expressed in watt-hours.

Cooling efficiency is indicated by the seasonal energy efficiency ratio (SEER), which is the total heat removed from the conditioned space during the annual cool­ing season, expressed in Btu, divided by the total electrical energy consumed by the heat pump during the same season, expressed in watt-hours.

The HSPF rates both the efficiency of the compressor and the electric-resistance elements.

The SEER rates a heat pump’s cooling ef­ficiency. In general, the higher the SEER, the higher the up-front cost. However, the energy savings can return the higher initial invest­ment several times during the heat pump’s life. A new central heat pump replacing a vintage unit will use much less energy, cutting air-conditioning costs substantially.

When choosing an air source electric heat pump, look for the ENERGY STAR® label. In warmer climates, SEER is more important than HSPF. In colder climates, focus on get­ting the highest HSPF feasible.

ASHP Rebates

How Air Source Heat Pumps Work

Air source heat pumps use the same tech­nologies that are found in refrigerators and air conditioners, and deliver cooling and heating by moving heat to and from the out­door air. During the summer when cooling a home, the ASHP works just like a central air conditioner, moving heat from inside the home and transferring it outside. An ASHP has the ability to reverse this process for heating: the ASHP harvests heat from outside air—some systems can provide heat­ing in temperatures as low as 0°F. The result is that homeowners are able to run their furnaces less and get extremely efficient heating from their ASHP.

Both ASHP heating and cooling can be con­trolled from a thermostat and the heating function is also able to work in tandem with conventional gas furnaces. The product au­tomatically selects an ideal balance between the two sources that maintains the most efficient heating combination.

ASHPs contain two sets of coils, a com­pressor, and a fan that circulates cooled or warmed air. The key to its ability to switch is a special reversing valve that changes the refrigerant flow’s direction, allowing the unit to seamlessly switch between air condition­ing and heating.

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