More
recently, even more advanced and efficient heating and
cooling systems have emerged using the geoexchange
process. Sometimes called geothermal or ground-source heat
pumps, these systems move or transfer heat like the
air-source heat pumps. However, they exchange heat with
the earth rather than the outdoor air.
Since
earth temperature remains relatively constant throughout
the year, geoexchange systems operate more efficiently
than air-source heat pumps and generally without the use
of resistance heat. And because they are working from
those constant earth temperatures, there are no blasts of
hot air or "cold blow" as with other systems.
Nearly
all geoexchange systems on the market have the ability to
provide low-cost domestic hot water, further increasing
their operating efficiency. Thus, geoexchange systems are
generally 2.5 to 4 or more times more efficient than
resistance heating and water heating alone, and have no
combustion or indoor air pollutants.
Since
there is no outdoor unit (as with air-source heat pumps or
the central air conditioners used with combustion-based
systems), no weather-related maintenance is required.
Although
their installation cost is somewhat higher due to the
required underground connections for heat transfer to and
from the earth, geoexchange systems provide low operating
and maintenance cost and greater comfort.