Choosing the Proper A/C for Your Living Space

Wall Air Conditioner

An air conditioner is a great way to escape the heat of summer and turn your home into a cool, comfortable environment. But not all homes have the same needs. Depending on your region and the size of your home, the strength and type of air conditioning system you require will vary.

How Many BTUs Do You Need? A Handy Chart

The US Department of Energy provides a chart for determining a room’s cooling needs.

First you must determine the square footage. For rectangular rooms, multiply the length by the width. For triangular spaces, multiply the length by the width, and divide by 2. These numbers represent the area of your room in square feet. (For example, a room 20 feet long and 12 feet wide is 240 square feet.)

The chart below will tell you the strength of the air conditioning unit you need, assuming your ceilings are 8 feet high. Rooms with higher ceilings will tend to need more A/C power, while those with lower ceilings will need less.

Cooling capacity is measured in BTUs (British Thermal Units), per hour, in tons.

Area to Be Cooled (in sq. ft.)      Capacity Needed (BTUs per hour)
100-1505,000
150-2506,000
250-3007,000
350-4009,000
400-45010,000
550-70014,000
700-1,00018,000

For economic reasons as well as energy efficiency, it’s important to select a unit that is the right size for your home. An air conditioner that is inadequate will not cool your home well, and will increase your electric bills; while an air conditioner that’s too strong will cycle off too often (leading to excessive wear and tear on the system) and not dehumidify the air properly.

Even though you’ve roughly figured out your home’s cooling needs, it’s important to consult a professional air conditioning contractor. Only he can properly factor in your home’s building material, level of insulation, and the number of windows in a given space. While your own estimate will help give you a ballpark figure of what you might expect to spend, an expert should help you make a final decision.

SEER Rating

The Seasonal Energy Efficiency Rating (SEER) is based on a scale from 10 – 16. Though a higher SEER level will increase the price of the unit, it will also mean a longer warranty and a lower utility bill. A unit with a lower SEER level may have a lower initial cost, but it will be much more expensive over time. If you live in a warm climate like Long Beach, where you will likely run the air conditioner for many months of the year, the SEER level can be a particularly important economical factor.

Type of Air Conditioner

Once you have an idea of your home’s cooling needs, you’ll have to choose the type of air conditioner you want. There are window units, which are used to cool an individual room; mini split air conditioners, which are capable of cooling several rooms; or central air units, which provide cool air throughout the house. Decide how many rooms you wish to cool and determine what option is the most efficient for you. Should you require a powerful air conditioner, consult with a licensed electrician to be sure your house has adequate amp capacity to supply the unit. If necessary, he can upgrade your wiring.

Whatever unit you choose, research and consultation will result in a better choice ... and ultimately a lower utility bill and a cooler, more pleasant home.

Updated August 8, 2018.

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