- Ideas & How-Tos
Choose Your Savings
Select the right air conditioner to cool off and save on energy costs with this buying guide.
Choosing the right air conditioner is easy with the right information. The first step, before you go shopping, is to learn to speak the language.
BTU: The British Thermal Unit (BTU) is the international measurement of energy. A BTU is the amount of heat required to raise 1 pound of water 1ºF Fahrenheit. In air conditioner (AC) jargon, a BTU measures the amount of heat an AC unit can remove from the room. As the BTU rating increases, so does the size, weight and cost of the AC. Room ACs are generally 5,000 to 24,000 BTU. Matching BTU requirements to room size is important. The room(s) won't cool efficiently if the BTU rating is too low or too high for the size of the room.
EER: The Energy Efficiency Ratio (EER) is calculated by dividing the BTU by the number of watts. The higher the EER number, the more efficient the unit should be. A higher EER-rated AC will also be more expensive, so decide if the higher price tag is worth the energy savings you may be getting. The ratings range from 8 to 11.5. If it's really hot where you are, go for a rating of 10 or higher.
Thermostat: The heat-sensing thermostat adjusts the temperature of the air coming from the AC unit. They can be programmable or manual. An adjustable thermostat combined with a variable-speed fan is an effective cooling machine. AC units are available with a remote control, 24-hour delay timers and digital temperature readouts.
Filter: Clean air is essential for efficient operation. Look for units with filters that can be easily cleaned or replaced.
Fan: The fan moves the air. A variable-speed fan combined with an adjustable thermostat is an effective cooling machine. Look for louvers that adjust up / down and right / left.
Chassis: The chassis is the frame that supports the main parts of an AC.
Packaged Terminal Heat Pump / Air Conditioner: This type of large heating or cooling unit, installed through the wall, is used in hotel and motel rooms.
Measure the Room
Determine the square footage of the room (multiply length x width).
There are lots of variables to consider when choosing a room AC: number of windows, number of people in the room, which direction the room is facing, ceiling height, etc.
This chart can help you find the right size room air conditioner to meet your needs.
Area to Be Cooled
(BTU per hour)
100 to 150
150 to 250
250 to 300
300 to 350
350 to 400
400 to 450
450 to 500
500 to 700
700 to 1,000
1,000 to 1,200
1,200 to 1,400
1,400 to 1,500
You may need to adjust the BTU rating needed based on whether the room to be cooled is sunny or shaded.
Most window air conditioners are designed to fit double hung windows. Measure the inside dimensions. Take an exact measurement, not just an estimation.
Take your room dimensions and window measurements with you when you go shopping.
What kind of plug does the unit have? What kind of plug is your wall outlet? Make sure the circuit can handle the operation of the unit. Smaller ones work with a standard 115-volt outlet. Larger 115-volt units may need a dedicated circuit. The largest AC units require a 230 / 208-volt circuit.
How heavy is it? Get some help when carrying and installing the unit. An AC unit can easily weigh over 100 pounds.
Although newer units are much quieter than older models, be prepared for some additional noise in the room.
Follow the manufacturer's instructions carefully when installing a window unit. It's essential that the unit be stable for safety reasons. It's also essential that the unit be tightly sealed to keep the cool air inside where it belongs. Apply weather stripping as needed to prevent airflow around the unit. Put the AC in a shaded window if possible for added cooling efficiency.
AC problems can be easily avoided with simple maintenance. Keep the filter and coils clean or replace them as recommended by the manufacturer. Don't need a new AC just yet? Here's some preseason maintenance advice for your old unit: