Geothermal Vs. Air Conditioner

Air Conditioning

• Air conditioners consist of a compressor, condenser and evaporator with a refrigerant circulating through the closed loop system. The compressor compresses the low-temperature, high-volume refrigerant vapor, changing it into a higher temperature, higher density vapor. The condensing coil then transitions the refrigerant into an even warmer and denser liquid. In the evaporating coil, the refrigerant expands and cools, cooling the surrounding air which then moves through the central duct system to cool a building.

Air-Source Heat Pump

• Air source heat pumps work in a similar fashion with one main difference: They have the capability to reverse the process to heat a building. A heat pump has indoor and outdoor coils. In summer, the indoor coil acts as an evaporator and the outdoor coil acts as a condenser, as in an air conditioner. In winter, a valve in the line leading to the condenser allows the flow of refrigerant to reverse, and the coils change roles, providing heat to the interior instead of cooling it.

Geothermal (Water-Source Heat Pump)

• Air-source heat pumps work well in mild climates, but they become less efficient in extreme temperatures because they rely on very high or very low outside air temperatures. Geothermal heat pumps instead use the more constant temperature of the earth's crust, several feet below the surface. The outdoor component of the geothermal heat pump is a long coil in the ground. To extract enough heat from the earth, or relinquish enough heat to the earth, the outdoor loop must be quite long, about 1,500 to 1,800 feet for a well insulated, 2,000-square foot home.

Comparison of Systems

• Air conditioning systems and air-source heat pumps are similar in cost, but geothermal systems are more expensive due to the cost of installing the ground loop, approximately twice the cost depending on the size of the ground loop and site conditions affecting installation. However, due to the efficiency of these systems, they reduce energy consumption dramatically, by 25 to 50 percent, and may pay for themselves in energy savings.

  An advantage of geothermal systems over conventional air conditioners is that the outdoor component, being below ground, is protected and has a life of 25 to 50 years or longer. And the pumps themselves are sturdy with a lifespan of 20 years or longer. Additionally, with no outside condenser, these systems are much quieter than air conditioners.