Terms to Know

HSPF —The Heating Seasonal Performance Factor or HSPF (the ratio of the seasonal heating output in Btus divided by the seasonal power consumption in watts) rates both the efficiency of the compressor and the electric-resistance elements. The most efficient heat pumps have an HSPF of between 8 and 10. Remember, when buying new equipment, sizing and installation are as important as product quality.

SEER — Cooling efficiency is indicated by the Seasonal Energy Efficiency Ratio or SEER (the ratio of the seasonal heat removed in Btus/hour to the seasonal power consumption in watts). In general, the higher the SEER, the higher the heat pump purchase price. However, the energy savings can return the higher initial investment several times during the heat pump's life. Replacing a 1970s vintage, central heat pump (SEER = 6) with a new unit (SEER=12) will allow the use of half the energy to provide the same amount of cooling, cutting air-conditioning costs in half. The most efficient heat pumps have SEERs of between 14 and 18.

Two-speed compressors — Unlike standard compressors that can only operate at full capacity, this type of compressor allows heat pumps to operate close to the heating or cooling capacity that is needed at any particular moment. This saves large amounts of electrical energy and reduces compressor wear. Two-speed heat pumps also work well with zone control systems. Zone control systems, often found in larger homes, use automatic dampers to allow the heat pump to keep different rooms at different temperatures.

Variable-speed or dual-speed motors — The variable-speed controls for these fans attempt to keep the air moving at a comfortable velocity, minimizing cool drafts and maximizing electrical savings. It also minimizes the noise from the blower running at full speed.

Desuperheater — Recovers waste heat from the heat pump's cooling mode and uses it to heat water. A desuperheater-equipped heat pump can heat water 2 to 3 times more efficiently than an ordinary electric water heater.

Scroll compressor —Consists of two spiral-shaped scrolls. One remains stationary, while the other orbits around it, compressing the refrigerant by forcing it into increasingly smaller areas. Compared to the typical piston compressors, scroll compressors have a longer operating life and are quieter. According to some reports, heat pumps with scroll compressors provide 10°–15°F (5.6°–8.3°C) warmer air when in the heating mode, compared to existing heat pumps with piston compressors.

Source Material: US Dept. of Energy

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