Sizing Air Conditioners

January/February 2010
A version of this article appears in the January/February 2010 issue of Home Energy Magazine.
Click here to read more articles about Cooling & Air Conditioning
January 07, 2010
A mountain of data leads to an unusual conclusion - sometimes bigger is not so bad.
Air conditioning is the cause of electric utility peak. Reducing that peak is a high priority for society, since producing and distributing peak electricity is the least effective use of limited resources. It is “common knowledge” that downsizing air conditioners makes them more efficient and reduces peak. If that common knowledge is true, and if the improvements are sufficiently large, then it appears obvious that downsizing should be investigated for every new air conditioner installed (see “Bigger Is Not Better: Sizing Air Conditioners Properly,” HE May/June ’95, p. 19). But common knowledge doesn’t always stand up to testing over time. Questioning Assumptions For energy efficiency: ▪ What is worse, an oversize house or an oversized air conditioner? ▪ What is worse, the unrepresentative SEER test or an oversized air conditioner? ▪ What is worse, a restrictive duct system or an oversized air conditioner? ▪ What is worse, an underinsulated ceiling or an oversized air conditioner? The answer in every case, heretical though it may seem, is that the oversized air conditioner is the smaller problem. In fact, it may be no problem at all. Traditionally, oversized air conditioners are considered responsible for significant excessive energy consumption. Changes in ...

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