How Air Conditioners Work
 
Air conditioners are constantly evolving to become user-friendlier and more energy-efficient. The way that they work is actually pretty simple. As warm air is passed through the cold coils inside your air conditioner, moisture is removed. Then the water vapour condenses on these coils and drains out of the air conditioner.

Look for a high-efficiency air conditioner. These units actually have variable speeds. Many have a fan setting that allows you to cool your house without using as much electricity. Then there are usually several other speeds ranging from low to high. The high speed setting cools the house very quickly but removes less humidity. Lower speed settings are slower at cooling your house, but remove more moisture, reducing the humidity in your house -- and this is what makes the biggest difference in how cool your house feels.

Temperature Controls
Some air conditioning units have electronic controls that allow for a more accurate temperature reading. This type can make your home more consistently comfortable because it makes it easier to find the temperature that is perfect, not too hot or cold. There are even models that include a built-in clock that can be set to start the air conditioning process before you wake up in the morning or before you get home from work.

Cooling Capacity

Size is Everything
Size matters. In fact, this is the single most important aspect to consider when you buy. If you choose a unit that is too big for your area, your house will feel damp and humid, not cool and refreshing. Another drawback is the oversized electrical bill you'll get at the end of the month.

The cooling capacity of an air conditioning unit is measured in BTUs (British Thermal Units). This is the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. You will see cooling capacities ranging from 5,000 BTUs all the way up to 18,000 BTUs. Taking some simple measurements will tell you which size is right.

Remember that instead of trying to cool the entire house with one huge unit, you may be better off buying several smaller units. The square footage of your room obtained by multiplying its length by its width. The rule for cooling capacity is:

Room Size (square feet)
BTUs

100-150
5000

400-450
10,000

700-1000
18,000
*If your room is very sunny, you may need a slightly larger unit.

Energy Efficiency Rating

A Healthier Electricity Bill
Manufacturers of air conditioners have been developing units that are easier on the environment and your pocket book. Believe it or not, air conditioners of the past could add up to sixteen percent of your annual electricity bill. These days, there is something called the Energy Efficiency Rating to make sure that your air conditioner uses less energy.

The important thing to remember about energy efficiency is that the higher the rating, the less electricity the air conditioner takes to cool your home. Air conditioners with a higher rating are more expensive to buy initially, but over time, they are actually the smarter choice. The extra money you pay when you buy the unit will end up paying for itself in saved electricity. Better than that, you can give yourself a pat on the back for doing something better for the environment.