Along with an air conditioner's EER (energy efficiency rating), many newer models are marked with an Energy Star label. These units work more efficiently and save more energy than other similar air conditioners.

In order for an air conditioning unit to earn an Energy Star Sticker, it must meet a very strict set of energy efficiency guidelines established by the U.S Environmental Protection Agency and the U.S. Department of Energy.

By replacing an old AC unit (that does not have an Energy Star rating) with a newer model that does have the Energy Star, you may be able to save up to $14 a year in electricity charges.

Energy Star portable and window unit air conditioners use at least 10% less energy than other conventional models. These units also typically include timers which allow for better temperature control as well as efficiency. Timers are a great feature for those who are away at work all day or typically out running errands. You can leave your AC unit during the time you are away and set your timer up to switch on your air conditioner an hour or so before you return, ensuring that no additional energy is wasted.

To get the best use of an Energy Star-labeled air conditioner, you should also make sure that you are purchasing a unit that is not too large for the space that you wish to cool.

You can figure out what size air conditioner you need by first determining the square footage of the room you plan to put the AC unit in. A good rule of thumb is to allow for 35BTUs for every square foot of a room. If the room you wish to cool is 216 square feet, multiply by that by 35 (216 x 35 = 7560) and purchase a unit that is as close to that number as possible. Buying a unit that is too large will actually cool your room LESS effectively than a properly sized unit and will waste more energy doing so.

In addition to keeping your energy bill down, Energy Star-labeled air conditioners help to prevent pollution and, in turn, global warming while promoting cleaner air as well. In addition to air conditioners with Energy Star labels, you should ensure that all of your future appliance purchases are also marked with Energy Saver stickers. Both the savings on your electricity bills as well as the positive environmental effects are well worth the investment.