central air conditioning illustration
Illustration: Harry Campbell
Central air-conditioning has always been the convenience people love to hate.

Despite the fact that it's standard equipment in most American homes — 88 percent of new construction and millions of retrofits every year — the systems have long been decried for the alarming amounts of electricity they devour, their ozone-depleting refrigerants, and the unseemly levels of noise generated by their condenser units, which rumble away just outside the house.

Happily, new AC technology means we can chill out about those worries. With improvements in fan-blade shape and compressor technology, some models make one-twentieth the noise of old units. A new refrigerant, known generically as R410A, is free of the chlorine that eats away the ozone layer. And energy use is on the decline. Twenty years ago, a typical system might use 6,000 watts of electricity per hour to cool an average-size house. Today, that same house can be cooled with as little as 1,710 watts per hour, an astounding 250-percent increase in operating efficiency.

A two-part (aka "split") system for cooling indoor air that consists of a condenser outside the house and an evaporator inside the house.

Refrigerant circulates in a closed loop between the evaporator and the condenser, capturing heat from the house and carrying it outside to a fan that blows it away.

SEER 13 or higher: SEER (seasonal energy-efficiency ratio) is like miles per gallon for a car: The higher the SEER rating, the better the system efficiency and the lower your electric bills. By law, the minimum SEER is 10; next year, it will be 13.
R410A refrigerant: Not only is it safe for the ozone layer, the compressors that use it are quieter than those using other refrigerants.
Low decibel rating: The quietest condensers have a rating of 68.
Diagnostics port: Permits a technician to quickly pinpoint and diagnose problems electronically.
Two-stage compressor: Operates at full power only on the hottest days.

$2,000-$4,000 (A SEER-13 system with condenser and evaporator for a 2,000-square-foot house, installed)

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