For climates with moderate heating and cooling
needs, heat pumps offer an energy-efficient alternative to furnaces and
Like your refrigerator, heat pumps
use electricity to move heat from a cool space into a warm place (heat
pumps powered by natural gas are also commercially available now).
During the heating season, heat pumps move heat from the cool outdoors
into your warm house; during the cooling season, heat pumps move heat
from your cool house into the warm outdoors.
Because they move heat rather than
generating heat, heat pumps can provide up to 4 times the amount of
energy they consume. If you heat with electricity, a heat pump can trim
the amount of electricity you use for heating by as much as 30% to 40%.
High-efficiency heat pumps also dehumidify better than standard central
air conditioners, resulting in less energy usage and more cooling
comfort in summer months.
If your home lacks a
ductwork system, you would need to add one to convert to a heat pump
system. Even if your house has ducts, you may need to modify them, as
heat pump systems generally require larger duct sizes than other central
heating systems. For proper heat pump operation, air flow should be 50
to 60 liters per second per kilowatt-hour or 400 to 500 cubic foot per
minute per ton of cooling capacity.
Consult a local heating and cooling contractor to assure that your
ductwork is sized properly.
The "conventional" model of heat
pump is the air-source heat pump, which transfers heat between your
house and the outside air. Although air-source heat pumps can be used in
nearly all parts of the United States, they do not perform well over
extended periods of sub-freezing temperatures. In regions with
sub-freezing winter temperatures, it may not be cost effective to meet
all your heating needs with an air-source heat pump.
Higher efficiencies are achieved
with ground-source (or geothermal) heat pumps, which transfer heat
between your house and the ground. Although they cost more to install,
geothermal heat pumps have low operating costs because they take
advantage of relatively constant ground temperatures. However, the
installation depends on the size of your lot, the subsoil and landscape.
If your house is located near a body of water, such as a pond or lake,
water-source heat pumps offer similar advantages. Ground-source or
water-source heat pumps can be used in more extreme climatic conditions
than air-source heat pumps, and customer satisfaction with the systems
is very high.