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Step 1
Determine the square footage of your home. This information is on the deed to your home. You can also measure this yourself by measuring each room in your home.
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Step 2
Pay attention to areas such as basements and attics when determining cooling needs for your home. Decide if cooling these areas is necessary.
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Step 3
Look up the BTU of central air conditioner. BTU means British thermal unit and is the unit most commonly used to measure heat energy. There are chart available for referencing how many BTUs you need for how many square feet of space.
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Step 4
Measure areas you don't plan on cooling separately, and subtract the square footage from the total to get the square feet of the space that you do plan to cool.
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Step 5
Remember that the outside temperature drops at night. However, you may want to use a small window unit in the bedrooms to avoid too much heat in rooms for sleeping. Again, measure the individual rooms to get the square footage, and then match that up to the BTU in the window cooling units.
