Air conditioners are basically just refrigerators, but they make the space outside them cool, while fridges keep the space inside them cool.

Air conditioners also work as dehumidifiers. Less humid air feels cooler.

The size of your home determines what type of air-conditioning system is best for cooling your home.

Most consumers are very price-conscious when purchasing an air conditioner. A split unit, used in most homes, costs thousands of dollars.

A window unit is an easy and affordable way to cool a small space. Choose a window to install it in and you're well on your way to chilling out!

In a split air-conditioning unit, the noisy compressor is located outside, and the air handler is inside the home.

There is no significant mechanical difference between a window unit and a larger split unit; they both operate the same way.

The filter is a very important part of the air conditioner because it cleans dust, pollen, mold and other allergens from the air. Be sure to change your filter frequently.

Some buildings have their air compressor on the roof. Have a look the next time you are taking off in a plane.

A British thermal unit (Btu) is the amount of heat needed to raise one pound of water one degree Fahrenheit. It's a standard unit of efficiency measurement in heating and cooling systems.

The higher the efficiency rating, generally the higher the price. A system with a high rating might pay for itself over time.

Chilled water air-conditioning systems are the least costly of these very expensive systems.

The most energy-efficient cooling system, and also the most environmentally friendly, is the ground source heat pump.

You can recoup the cost by saving money on your electric bill, but it may take several years to do so.

Passive cooling is a method of cooling your house without an air-conditioning unit. Some passive cooling methods include heat shielding, landscaping, ceiling fans and good insulation.

A popular passive cooling method is to open windows and create airflow. Let some fresh air in!

Apartment buildings and other multifamily homes have a compressor for each living unit.

Large campuses such as a university have a central cooling unit and run pipes with chilled water to different air handlers.

Ice cooling is a new "green" type of air-conditioning. It involves freezing water into ice overnight when electricity rates are lowest and then blowing fans over the blocks of ice.

As of 2007, there were more than 3,000 ice coolers worldwide, according to New York state officials. They're expensive to install but help reduce air pollution and are easier on the power grid than traditional air conditioners.