The perfect way to cool down a room in your home is by using a window air conditioner. This type of air conditioner can keep a room cool and humidified at the same time. However, before you head off to buy a new unit, you’ll need to figure out what size you need. You see, window air conditioners come in different sizes, or cooling capacities. The cooling capacity of a unit is measured in British Thermal Units, (BTU’s). The more BTU’s it has, the more space it can cool down. And, of course, the bigger the room, the more BTU’s you’ll need. If you buy a window air conditioner that is too big, it will start and stop too much. This will not only waste energy, but your room won’t be properly dehumidified. On the same hand, an air conditioner that is too small for your room will run too much trying to do its job. If the unit doesn’t have enough BTU’s, the room never will become cool and comfortable.

So, how do you figure out what size of a window air conditioner that you need? There’s a sure-fire formula that will take many factors important into consideration. First, measure the length of the room you want to cool down. Then, measure the width of that same room. Finally, measure the height of the room from the floor to the ceiling. Multiply the length times the width times the height. The resulting number is the volume of the room.

Now, you’ll need to determine which direction the most exposed wall of the room faces. That is, which wall of the room is most exposed to the outside elements. Look around the room to find the answer- is it east? north? south? or west? Look at east as having a value of 17; west as having a value of 20; north’s value is 16, and south is 18. Use the volume of the room and multiply that number by the corresponding number for whatever direction you chose.

Finally, in order to find out what size of a window air conditioner you’ll need to buy for your room, divide the result you last arrived at by the number which corresponds most accurately to the level of your home’s insulation. If your home has poor insulation, use a 4. If the insulation is good, use a 5. And, if the insulation in your home is excellent, then use the number 6.

The result of these calculations will give you the approximate number of BTU’s your new air conditioner will need to have.

Does the formula sound complicated? It’s really not. All the numbers in the calculation are necessary. That way, the volume of your room, the exposure of the outside elements, and the rating of the insulation are all taken into consideration.

Let me give you the example of my living room. I purchased a window air conditioner for this room, and the formula gave me the perfect size. My living room is 20 feet long, 18 feet wide, and 8 feet high. I multiplied 20 by 18 by 8 which equals 2,880. The wall that is most exposed to the outside elements is the south side. The corresponding number for south is 18. So I multiplied the 2,880 by 18. The result is 51,840. Next, I determined that the insulation level of my home is good. A “good” level is a number 5. Finally, I divided 51,840 by 5. The resulting number is 10,368. After I rounded it off, this told me that I needed to purchase a 10,000 BTU air conditioner. They come in sizes from 5,000 BTU’s all the way up to 24,000 BTU’s.