Many people mistakenly believe that "the bigger the better" is the mantra to follow when it comes to air conditioners. It would seem logical that larger, more powerful AC units would translate into cooler, more comfortable rooms.

In truth, if you purchase an air conditioning unit that is too large or powerful for your space, you will actually create more of a problem for yourself.

The general rule of thumb states that you should allow 35BTU for every square foot of a room. If you wish to cool a room that is 12 x 18 (or 216 square feet), multiply 216 x 35 = 7560. You should try to find an air conditioning unit that is close to 7560BTUs as possible.

By ensuring that you are purchasing an air conditioning unit that is correctly sized for your space you will find several immediate benefits:

• After measuring your space, you will not waste any money on a unit that is too large for your space.
• Using a properly-sized air conditioning unit will keep your energy bills at their most efficient levels, as your compressor will be running constantly.
• You will find that your room will maintain more even temperatures as your AC unit will run more regularly, rather than constantly cycling on and off.
• A properly sized AC unit will not create any extra noise in your space.

Keep in mind that window-sized air conditioning units, even the larger models, are only meant to cool limited spaces. Another common mistake people make is to purchase a gigantic air conditioning unit that they hope will cool their entire house or apartment. You are always better off purchasing several smaller units for each room, rather than one large unit. This will also give you much greater control of your temperatures (and allow you to vary them room by room) as well as your energy bills.

Check the labels and tags of any air conditioning unit you wish to purchase. The recommended room size for each unit is normally listed and will allow you to make the best purchase for your space possible. A properly sized air conditioning unit will be much easier for you to install and maintain, and will provide you with exactly the sort of cool comfort you will appreciate on a hot summer day.