Purchasing An Air Conditioner

The decision to buy a new air conditioner should be accompanied by a commitment to do some research and planning first. While you will pay once for the unit up front, you will live with its utility bills for as long as you own it. Therefore, take more than first cost into consideration. Air conditioners include window units, whole-house units, evaporative coolers, and heat pumps.

Window units are great if you only have one or a few small rooms to cool. They require no special ducting or wiring. When you shop, be sure to look for EnergyGuide labels and compare energy costs for comparable units, and look for units displaying the ENERGY STAR® logo indicating they are more energy efficient and environmentally friendly. Once you've selected one, install it into the window, and plug it in to the standard house electrical outlet.

Whole-house units are more complicated and usually purchased through a contractor who will look at the size of your house, the climate, and your cooling loads to determine what size unit to specify. They may be a problem if your home does not have ductwork to carry the cooled air throughout your home. Adding them can be an expensive retrofit. In working with a contractor to select a whole-house system, you'll need to emphasize your interest in a high-efficiency unit as indicated by a SEER (seasonal energy efficiency ratio) of 13 or higher. Systems are called split-systems when they consist of an outside part housing the compressor and coils, and an indoor unit containing the cooling coils and air handler. Your first concern in locating the outdoor unit may be to avoid hearing the noise it makes, but in addition, try to locate it in a shady spot on the north side of the home to keep it cooler. It works more efficiently exchanging its heat when in a cooler place.

Evaporative coolers that work by blowing air over a moist pad only work well in hot, arid climates. Where they will work, they do save money. They cost about half what a conventional air conditioner does and less than a quarter as much to operate.

Heat pumps are convenient because they provide both heating and cooling in a single unit. In the summer, they work like an air conditioner. In the winter, they reverse to become air heaters, transferring heat from outside the home to the inside. Naturally, they are more expensive than a simple air conditioner, but they make sense when you need both heating and cooling.

Today's heat pumps are not like those of the 70's. Even at 30º F. today's heat pumps are around 280% efficient. Straight resistance heating offers 100% efficiency, while natural gas, propane and other sources are at 90% or less. At 17º F. a heat pump is still around 256% efficient. (Efficiencies will vary based upon unit seasonal energy efficiency ratio [SEER] and coil size.)

A heat pump can mean savings of 30 to 60 percent on electric heating bills because it uses 30 to 60 percent less energy to supply the same heat as an electric furnace with a resistance heating element. Engineers refer to this advantage of the heat pump as the Heating Seasonal Performance Factor (HSPF). The higher the HSPF, the more efficient is the unit.