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Window air conditioners are an economical alternative for those apartment dwellers and homeowners who don't have the luxury of a central air conditioning unit in their homes.

Purchasing the right-sized air conditioner is essential in two ways. One, you need to purchase a large enough unit to cool the entire area of the room you are going to install it in. If it runs too long,trying to cool down too large of an area, your air conditioner will probably sustain damage. But, two, if you purchase a unit that is considerably too large to cool the room, you will waste electricity and spend money unnecessarily. Of course, the larger the unit, the bigger
the price tag will be. Also, the room you are attempting to cool will cool off too quickly and the humidity will not be removed from the air. So, purchasing exactly the right unit for your needs is the wise thing to do.

An air conditioner's cooling capacity is measured in Btu's, or "British thermal units" per hours it operates. The Btu if an air conditioner must match the size of the room you are installing it in. First, you will need to measure the length of the room, the width of the room, and the height of the room from floor to ceiling. Next, multiply the length times the width times the height. The result is the volume of the room.

Next, figure out which direction the most exposed wall of the room faces: East, West, North, or South.

Then, multiply the room's volume by the corresponding number: East-17, West-20, North-16, and South-18.

Finally, divide the result by the number which corresponds most accurately to your home's insulation: Poor insulation-4, Good Insulation-5, or Excellent Insulation-6.

The result of these calculations will give you the approximate Btu's your new air conditioner needs to be.

Let's look at an example in order to clarify the above:

Example- You want to air condition a room in your home that is 20 feet long, 18 feet wide, and 8 feet high. That would be 20 times 18 times 8 which equals 2,880. The wall that is most exposed to the sun and other elements faces the South. South's corresponding number is 18. Now we multiply 2,880 by 18 which equals 51,840. Next we determine that the home's insulation is good which corresponds to a number 5. Finally, we divide 51,840 by the number 5 and we find that the resulting number is 10,368. This tells us we need to purchase a 10,000 Btu air conditioner.

Just by doing a few simple calculations, you will quickly find out how big or small of a unit you need. Then you can rest assured that you have purchased the best air conditioner to do the most efficient and economical job for you.