Many people living in South Florida actively seek shade. Its a tradition. Studies have shown that most people in Florida, when it comes to parking, if they can park in the shade, they will walk farther.
So it follows that most people would conclude that when the question arises of shading or not shading your air conditioner, most people assume that SHADING is a good idea. It seems to be a simple matter of common sense. Get out of the sun. “Only mad dogs and Englishmen are out in the noonday sun“. But we know, that “gut instinct” doesn’t always provide the same quality information as science.
First lets make sure we’re talking about the same thing. The box that sits outside your house, is called the “condensing unit” that houses cooling tubes, and performs a heat exchanging process (think radiator). It serves as both an exhaust port and an intake port, in addition to being the home of the cooling tubes. You might know it as the noisy fan box. So as the cooling tubes act as a heat exchanger, cooling the indrawn air and exhausting out the hot air. So this box, acts as your air conditioners lungs as it both “inhales” and “exhales” the outside air that gets “conditioned”. This ultimately becomes the crux of the matter. Our answer to the question: to shade or not to shade, will derive more from the air, intake and exhaust, more than it is about a a metal box, sitting in the noon day sun. Which can seem a little counter intuitive at first.
Well after years of debate scientists decided to carefully research the question in the field. Who ? The EPA has issued a study suggesting that people should shade your outdoor air conditioning system with landscaping or other shading system as a technique that would reduce the energy use (Akbari et al., 1992).
Then testing was conducted in Florida by the FLORIDA SOLAR ENERGY CENTER (F.S.E.C.) at the University of Central Florida. They decided it was time to end the debate, and actually answer the question with a series of real world experiments. These experiments will finally answer the question could shading your outdoor air conditioning unit help lower energy use? They the (F.S.E.C.) did a before-and-after experiments at three different residences, over two years.
The theory most people operate under is when I’m in the sun, I’m hot. If my air conditioner sits in the sun all day long, it must have an impact. Therefore providing shade for your air conditioner’s outdoor condenser will reduces your energy costs ? But does it, under scientifically controlled conditions in the field. We’ll see.
Tests showed that even avoiding impeding both the exhaust flow, and the intake port, the impact on cost was approximately 1%. Not actually significant. The ultimate point of the study was that because the volume of air being drawn into the unit goes largely uneffected by simply shading the box. Therefore shading the box, makes almost no impact.
The actual equation looks like this:
Although the peak solar intensity may be approximately 1,000 W/m2, the required condenser air flows which are greater than 600 cfm per ton will tend to reduce the importance of this effect.
For instance a typical 3-ton condenser will process 170,000 cubic feet (4.81 x 106L) of air per hour with a total density-specific heat product of 3,060 Btu/oF
The peak solar intensity is roughly 1000 Watts (think light bulb) per meter squared, the air flow equals over 600 cfm (Cubic Feet per Meter) So the heating impact of the sun, is completely overwhelmed by the volume of hot air drawn in. Cool a large area of air, around the unit, and you might have an impact, otherwise its far more important to make sure the exhaust fan does its work unimpeded.