In this article:

• Types of Air Conditioners
• Central Air Conditioners: The Ozone Issue
• Sizing a Central Air Conditioner
• Central Air Conditioner Energy Efficiency
• Central Air Conditioner Cost Considerations

An unbiased, expert consumer report on how to buy the best central air-conditioning system for your home.

By Don Vandervort, HomeTips

On a hot, humid summer day, few amenities add to quality of life more than home air conditioning. An air conditioner cools, dehumidifies, and filters your home’s air, making it cleaner and far more comfortable. This is, no doubt, why central air conditioning has become common in homes located in warm climates.

Types of Air Conditioners

Unlike a window, portable, or in-the-wall air conditioner, which cools a single area, a central air conditioner distributes conditioned air throughout a house. It has a condenser unit that sits outdoors, a central air-handling unit such as a forced-air furnace or heat pump that is typically located in the basement or attic, and ductwork routed throughout the house for delivering cooled air from the air handler.

A heat pump is related to an air conditioner. It is essentially a central air conditioner that can be reversed in winter to heat a house. Both air conditioners and heat pumps use refrigeration technology to achieve the transfer of heat or cold. (For more information about how refrigeration works, see How a Central Air Conditioner Works.)

The first decision you will face when choosing an air conditioner is whether to opt for a whole-house air conditioner, one or more room air conditioners, or a heat pump. (For more information on the pros and cons of each, see Air Conditioners: Central or Portable?)

Central air conditioning is the most popular of the options, particularly for a home that is equipped with a forced-air heating system or, even better, an existing whole-house central air conditioner.

Central Air Conditioners: The Ozone Issue

If you’ve kept up with consumer reports, you may be aware that the refrigerant used in some air conditioners has been targeted as an ozone-depleting substance. The problem is that aging, sealed systems may develop leaks and allow the refrigerant to escape into the atmosphere.

Prior to December 31, 1995, a common refrigerant in older cars, some commercial air conditioners, and certain refrigerators was CFC-12, or R-12. Now, the commonly used refrigerant in home air conditioners is R-22, an HCFC (hydrochlorofluorocarbon) that is safer but can still be a problem if it reaches the stratosphere. Production of HCFCs will be phased out eventually, too.

The refrigerant used in new car air-conditioning systems is R134a, an HFC (hydrofluorocarbon) that does not contain ozone-damaging chlorine atoms. Carrier was the first manufacturer to produce a residential central air-conditioning system—the WeatherMaker 134a—that uses this refrigerant. Other manufacturers are also introducing similar systems.

Sizing a Central Air Conditioner

Manufacturers produce whole-house central air conditioners in a range of sizes, which raises one of the most important questions you’ll have to answer when shopping for one: How big should it be?

HomeTips Pro Tip: You want a central air conditioner to be large enough to cool your home, but you don’t want to spend more than necessary for the equipment and you don’t want the unit to be so large that it operates inefficiently. (For more on how to choose the right size central air conditioner, see Central Air Conditioners: Cooling Capacity.)

Central Air Conditioning Energy Efficiency

Air conditioners are expensive to operate because of today’s high cost of energy, so it doesn’t make sense to buy one that you can’t afford to run. The name of the game is efficiency—an air conditioner’s ability to convert energy (electricity) to cooling in the most cost-effective way. Every new air conditioning unit is given an efficiency rating, called a SEER (Seasonal Energy Efficiency Rating). This is listed on the yellow Energy Guide label posted on each unit. (For more about energy efficiency, see Central Air Conditioners: Energy-Efficiency Ratings.)

Central Air Conditioner Cost Considerations

Installing a central air conditioner is not a do-it-yourself project, so you should discuss the following with a qualified air-conditioning contractor:

First, find out whether your house can readily accept an air-conditioning system. Installing one usually only makes sense if a house is being newly constructed or has a forced-air heating system that the air conditioner can piggyback on. Retrofitting the needed ductwork is simply too expensive in most cases.

Even in a home with usable ductwork, a standard central air-conditioning system can cost $3,000 to $6,000 or more installed. Because the cost depends on so many variables, the only way to pinpoint it is to get at least three bids. (For more about air conditioner costs, see Central Air Conditioners: Cost Considerations.)

And, if you are replacing an aging system, be sure to replace both the outdoor condensing unit and the indoor evaporator. If you just replace the condensing unit, potential gains of a higher-efficiency unit may be lost.