An air conditioner's condensing unit dumps heat from the house into the outdoor air. Will shading the unit lower your energy bills? I got a question this weekend that's often asked — and, I'm sure, wondered about — by homeowners: "Will my household AC system run more efficiently (perhaps cycle on/off fewer times, or the compressor won't have to run as long when it cycles on) by shading the compressor?" I've written about the outdoor unit of air conditioners and heat pumps a few times, but I've never tackled this question directly. If you have a split-system air conditioner, that metal noisemaker that sits out in back or on the side of your house is called the condensing unit. (To understand how an air conditioner works, see my article, "The Magic of Cold.")(If you have a ground-source heat pumpHome heating and cooling system that relies on the mass of the earth as the heat source and heat sink. Temperatures underground are relatively constant. Using a ground-source heat pump, heat from fluid circulated through an underground loop is transferred to and/or from the home through a heat exchanger.

The energy performance of ground-source heat pumps is usually better than that of air-source heat pumps; ground-source heat pumps also perform better over a wider range of above-ground temperatures., that heat gets dumped into the ground rather than the air, and you won't have an outdoor unit like the one shown above.) The Difference Between Air Conditioners and Dehumidifiers Hence the question: Can shading your air conditioner's outdoor unit provide significant savings? The answer is yes and no. Shading the outdoor unit with a structure as shown in Image #2 (below) will reduce the direct solar gain from insolation but won't do a whole lot for the air temperature around the unit. Caution: The unit in the photo exhausts from the side, so the shading structure doesn't interrupt the air flow. In the "Discussion" section at the end of their report, the FSEC authors explain why small-scale shading like this doesn't work. A typical 3-ton air conditioner condensing unit might pull in 2,800 cubic feet per minute (cfm) of outdoor air.

Even at 30 minutes per hour, though, the outdoor unit pulls in 84,000 cubic feet of outdoor air. To put those numbers in perspective, 84,000 cubic feet is about three times the volume of a typical house being cooled by that 3-ton air conditioner. If you’re building a new home or siting a new air conditioner, it’s worth considering the location of the outdoor unit. If you could save even a little bit just by putting it on the north side of the house, that might be worth doing. I say "might" because you also have to consider the effect on the length of the refrigerant lineset and whether or not it’s in a high-use area of the yard. If you’ve got an existing home, however, trying to figure out a way to shade your outdoor unit isn’t the best strategy. You might even make things worse if you obstruct the air flow. A question related to the question about shading the condensing unit is about saving money by spraying a mist of water on the unit, especially with the recent launch of the Mistbox.