Efficient HVAC Systems: Ground Source vs. Air Source Heat Pumps

efficient-hvac-systems-air-source-heat-pumpWhen it comes to heating and cooling energy efficiency, the term “heat pump” is often referred to by those within the industry. However, most homeowners don’t know what a heat pump is or how they actually work. It helps to first understand the differences in these two different efficient HVAC systems:

An air source heat pump (ASHP) is a central system that harvests heat from the outside air, which is then circulated through the house’s ductwork by the furnace or air handler to heat the home during the winter months. During the summer months, the cycle is reversed. Heat is taken from inside the home and then rejected to the outside. This process is known as air conditioning. It is all about the movement of heat.

A ground source heat pump (GSHP) also commonly known as geothermal heating and cooling, is a central system that in winter months collects the Earth’s natural heat through a series of pipes installed below the surface of the ground, called a loop field. Fluid circulates through the loops and carries the heat to the house. There, an electrically driven compressor and a heat exchanger concentrate the Earth’s energy and release it inside the home at a higher temperature. Ductwork then distributes the heat to throughout the home. In summer months, the process is reversed. The underground loop draws excess heat from within the home and allows it to be absorbed by the Earth. The technical terminology for this process is “heat of extraction” (winter months) and “heat of rejection” (summer months).


Installation Differences

The installation of an ASHP has the same installation time as a regular heating and cooling system 1-2 days and you are up and running. On the other hand, GSHP is a big process that includes applying for digging permits and the coordination between the loop contractor and the heating contractor. For a smooth process always look for an experienced contractor who is not new to geothermal technology. The last thing you want is to spend that much money on efficient HVAC systems and not have you new system work at peak capacity.

Efficient HVAC Systems

There is no question, GSHP are more efficient than ASHP due to the constant temperature below the earth’s surface. The reason why ASHP efficiency varies is because the outside air fluctuates from day to day. It is safe to say that both heat pump methods are by far more efficient than burning natural gas or propane furnaces.

Dual-fuel systems

For some homes, an air source heat pump can be paired with a gas furnace to create a dual-fuel or hybrid system.  In this configuration, you enjoy the best possible balance between comfort and energy efficiency. Because electricity is typically cheaper than gas during certain months of the year, this means a more energy-efficient comfort.

✔ In cool weather, when the season transitions from summer to fall, the heat pump in a dual-fuel system would keep the home warm.
✔ When winter arrives and the weather becomes colder, it would take substantially more electricity to draw in enough heat to keep the home warm. So the dual-fuel system would switch from the heat pump to the gas furnace mode to provide warmth.

Which heat pump should I choose?

The decision to choose a heat pump for a home has to do with the climate in which the home is located and your financial state. Air-source heat pumps typically work better in warmer southern climates where winters aren’t too harsh. Ground source heat pumps will work anywhere you install one, northern and southern climates, due to the constant temperature below the earth’s surface. GSHP do typically cost 2-3 times more than an ASHP, but the return on investment (ROI) is better with the purchase of a GSHP.

I always suggest contacting an experienced heating and cooling contractor to get the energy-conscious advantages of the different heat pumps for your home, or to discuss the year-round advantages of a dual-fuel system.

Author: Joe Tollari