Ground-source heat pumps use relatively stable underground temperatures to heat and cool a home, and to supply hot water.
Because heat pumps are the most efficient electric heating and cooling technology, they are an excellent choice if your home needs a heating, ventilation and air conditioning (HVAC) upgrade. While electric resistance heaters may be 100 percent efficient — meaning all the electricity that goes into it is used to generate heat — heat pumps can offer efficiency of 200 percent to 400 percent.
But the proper heat pump for your home depends on a variety of factors. Following are some tips when considering air-source and ground-source heat pumps.
There are two main types of air-source heat pumps: ducted and ductless. Both provide heating and cooling, and they can also create hot water.
In cooling mode, these appliances function similar to an air conditioner by moving heat from inside to outside your dwelling. In heating mode, the refrigerant flow is reversed and produces warm air indoors.
When outdoor temperatures drop, the efficiency of air-source heat pumps decreases. As a result, these pumps are most popular in areas of the country, such as southern states, that do not experience extremely cold weather for extended periods. A good rule of thumb for air-source heat pumps is that they are effective until the thermometer drops to the 35–42 degrees F range. Heat pumps do continue to supply heat well below freezing temperatures, but may not be able to supply an entire home's heating requirements without help from a supplemental source.
For residents in the northern U.S., dual fuel setups can be attractive — which combine an air-source heat pump with a natural gas-, propane-, or heating oil-fired furnace. In those climates, a heat pump warms a house during fall, or warmer winter days and the spring months. When a prolonged cold snap hits, the supplemental furnace takes over.
Ducted systems have been the traditional air-source heat pump route, but ductless systems are picking up steam because they require less electricity than electric resistance heating — an estimated 50 percent to 60 percent less. In addition, air-source heat pumps that achieve Energy Star designation — meaning they meet or exceed federal energy efficiency standards — can be up to 9 percent more efficient than standard air-source heat pumps. The very nature of ductless heat pumps usually promotes zonal control of their operation, thus saving even more money when rooms are not occupied and the heating or cooling zone can be shut off.
Ground-source heat pumps, also called geothermal heat pumps, use relatively stable underground temperatures to heat and cool a home, and even to supply hot water. They come in two types: A groundwater (open-loop) heat pump uses well water, while an earth-coupled (closed-loop) model moves a water-and-antifreeze solution through underground pipes to disperse or absorb heat. The choice depends on local conditions.
Ground-source heat pumps tend to be the most efficient heating and cooling technology available, but the up-front cost is significantly higher than air-source heat pumps. The final price tag depends on where you live and the location and type of your loop system. A typical residential consumer selecting a geothermal system will save 30 to 60 percent or even more on an average heating and cooling bill compared to the cost of an air-source heat pump.
Consult your electric co-op
Choosing a heating and cooling system for your home is a big decision with lots of variables. Be sure to call your local electric cooperative for advice on what type of unit will work best for your area, and ask if your co-op offers any incentives for installing a high efficiency heat pump or geothermal system. Then, contact a reputable and knowledgeable HVAC contractor to discuss your options.