Depending on where you live, an air conditioner might be needed to help you through the warm months of the year.

Taken literally, air conditioning includes both the cooling and heating of air, cleaning it and controlling its moisture level, and conditioning it to provide maximum indoor comfort. However, for our purposes, we'll refer to air conditioning as the process of cooling air for comfort.

Home comfort isn't a new idea. As far back as the ancient Egyptians, Greeks and Romans, people have been trying to control their environment. Early civilizations used air blown over wet mats to cool their homes. British miners improved their working conditions in the mid-16th century by using then-new ventilating fans. In 1902, mechanical cooling equipment began to appear in buildings in New York City. Thirty years later, what had become known as "air conditioning" was first used in homes and apartments.

An air conditioning system is a lot like an automobile efficiency depends greatly on the way it is maintained and operated. Cars get better mileage and last longer when they get proper care and attention and are driven moderately. The same is true of air conditioning systems. If you have a system and can locate the manual, consult it to find ways to operate your system most efficiently.

Air conditioning systems do more than just cool the air. They lower humidity, and also remove dust and dirt by moving the air through filters. When these filters become clogged with dirt, the system must work harder to do its job. This wastes energy and inflates utility bills. Disposable filters should be checked every two months (once a month during peak use) and replaced when necessary. Permanent filters should be cleaned in accordance with the manufacturer's instructions.

Some people like to "help" their air conditioner by opening doors and windows on warm days. But doing so lets all the cool, dehumidified air rush outside and lets in the hot, humid air. The more your home seals out heat, humidity, and dust, the more efficiently your system will do its job. Insulation, weather-stripping, window coverings and shade trees are a few things that can be used to help your home beat the heat.

The useful life of an air conditioner can vary greatly. Factors such as climate, maintenance care, and quality and capacity of the original equipment can increase or decrease the service a system will give by months and even years. On the average, a residential central air conditioner will last from 10 to 15 years. When a unit begins to show its age, it is usually major components such as motors or the compressor that wear out. In the short run, replacing failed components will usually cost the least amount of money. But, in so doing, an opportunity to greatly improve the overall efficiency of the system could be lost.

In recent years, air conditioner manufacturers have made dramatic progress in increasing the efficiency of the units they produce. Therefore, it might make more economic sense to put the cost of repair into a new, more efficient unit that will bring down operating costs. Eventually, the more efficient unit should pay for itself through decreased utility bills. What's more, the new unit will be more reliable and offer warranty protection.

The size of an air conditioning unit is best determined by a heating and cooling professional contractor. A properly sized unit can ensure maximum comfort and efficiency. Too large a unit will cool the space but will not run long enough to remove humidity. The result will be a cold, clammy environment within the home. A unit that is too small might mean that you will not attain the degree of coolness you want on very hot days, no matter how long the system runs. Hence, a thermostat set at 78 degrees might only be able to reduce the temperature to 85 degrees on especially hot days.

If you walk into your home and find it stifling hot because the air conditioner was turned off, don't be tempted to move the thermostat to a very low setting to cool the house faster. Setting the thermostat lower than usual will not produce more or colder air. It's best to leave the thermostat alone while the system is running. Constantly setting the control up or down might waste significant amounts of energy.

At night, or when you'll be away from the house for extended periods of time, you probably will want to make energy-saving adjustments to the thermostat setting by raising the desired temperature. But for normal daytime activities, find a comfortable level and leave the thermostat at that setting. "smart" or programmable thermostat is an element that can help you get the most from your heating and cooling system.

For more money-saving air conditioning tips, write the Air-Conditioning and Refrigeration Institute (ARI), 4301 N. Fairfax Drive, Suite 425, Arlington, VA 22203. Include a self-addressed stamped business size envelope, and they'll send you an information-packed 31-page booklet FREE!