Air Source Heat Pumps

When “heat pumps” are mentioned in the media, the reference is usually to geothermal, or ground source, heat pumps. A geothermal system absorbs heat from the ground and releases it in your home. But there is another type of heat pump: the air source heat pumps. Air source heat pumps are the original heat pump, and they are still installed several times often as geothermal systems.

An air source heat pump is basically just a central air conditioner that runs backwards in the winter. It is capable of “pumping” heat from the cold outdoor air into the warmer indoor air in the winter, just like an air conditioner pumps heat from the cooler indoor air into the hot outdoor air during the summer.

Unlike furnaces and boilers, which produce all of their heat energy from the fuel they burn, a heat pump only moves heat. When the outdoor temperature is only a few degrees below room temperature, an air source unit can operate at about 450% efficiency. This means it can provide about 4.5 watt-hours of heat energy for every watt-hour of electricity it consumes. A few degrees above freezing, it’s efficiency will drop down to about 200%. As temperatures drop below freezing, the unit will become ineffective as there is too little heat in the air to extract.

Comparatively, a geothermal heat pump can provide heat at about 400% efficiency at any time, even the coldest days of the year. However, installing a geothermal system, complete with 500-2000 feet of piping under the ground, usually costs several times as much as installing an air source unit.

So you’ve probably figured out by now that an air source unit will work well in areas that require enough energy for heating so that there is a substantial potential for energy savings, but not so cold that temperatures are often below freezing. In areas where the winters are below freezing for weeks on end, geothermal units should be considered.

When determining how much you can save on energy with a heat pump (air source or geothermal) two other important factors are: the cost of electricity in your area (5 cents per kilowatt hour is low, over 10 cents is high) and your current method of heating (you’ll save more if you’re currently using an older furnace and especially if you’re using an oil furnace).

More information:

Natural Resources Canada’s Heat Pump Guide

U.S. Department of Energy Heat Pump Guide

www.housesmartheating.com/heat-pumps