Size matters when you’re buying a window air conditioner. Buy too small and it will struggle to keep the room at a comfortable temperature; buy too big and and the room will cool too quickly without removing enough humidity from the air. Buy just right and you’ll be comfy and save money too. At Consumer Reports, we test air conditioners in the size rooms that they're intended to cool. Here are the best small, medium, and large window air conditioners from our tests. Bedroom or office (100 to 300 square feet) For a small bedroom, home office, or guest room you’ll want an air conditioner with good scores for comfort and quiet. The GE AEM05LV, $170, a CR Best Buy, aced our comfort tests and was very quiet on both low and high fan speeds. The LG LW6016R, $175, was also excellent at cooling a small room and was very quiet on the low fan setting but a little nosier on high. The Frigidaire FFRA0511R1, $125, was a little nosier but the price is right. Master bedroom or playroom (250 to 400 square feet)

To cool a bigger or busier room, you’ll want to step up to a mid-sized air conditioner. The GE AEM08LT, $300, was tops in its class with excellent scores for cooling a medium-size room. world's smallest window ac unitIt cruised through our brownout test, which tests if a unit can restart when voltage is low.  cost of high efficiency ac unitBut it was a bit noisy when the fan was on high.ac window unit sale The LG LW8014ER, $240, a CR Best Buy, has very good scores for cooling and aced the brownout test.  It was also somewhat  noisy with the fan was on high. Living room or family room (350 to 650 square feet) For a living room or family room, you’ll want a large air conditioner, especially if you have an open floor plan.

The LG LW1214ER, $350, made our top picks list with its excellent scores for comfort. And despite its size, it operates at a quiet hum. The Haier HWE12XCR, $310, was excellent at cooling but nosier than the LG. But it bounces right back in brownout conditions. Size up your needs Window air conditioners typically have cooling capacities ranging from 5,000 to 12,500 British Thermal Units (BTUs). But don’t buy by BTU alone. As a rule of thumb, an air conditioner needs 20 BTU for each square foot of living space but there are other considerations such as the height of your ceiling and the size of your windows and doorways. Energy Star recommends that you make adjustments for the following circumstances: If the room is heavily shaded, reduce capacity by 10 percent. If the room is very sunny, increase capacity by 10 percent. If more than two people regularly occupy the room, add 600 BTUs for each additional person. If the unit is used in a kitchen, increase capacity by 4,000 BTUs.

To get the most from your window air conditioner, install it right. If your window is not in the center of your room, check that the direction of the airflow is into the room, not into the corner. Here are some tips from EnergySavers.gov. Make sure it’s level so the drainage system works effectively.Some larger units need a dedicated circuit. Don’t put lamps or TVs near the air conditioner’s thermostat as the heat will cause it to run longer. Set the thermostat as high as is comfortable, typically 78° F. You’ll appreciate the savings. Don’t dial the temperature down when you turn the air conditioner on—it won’t cool the room any faster. On humid days, set the fan speed on low; the slower air movement removes more moisture from the air. Use an extra fan to spread the cooled air around. Energy standards for window air conditioners are getting tougher, making them cheaper to run. Look for an Energy Efficiency Ratio of 10 or above. The higher the EER, the more efficient the air conditioner.

Look for models with filters that are easy to remove for regular cleaning. All the air conditioners in our tests have remote controls, digital displays, and timers that you can set to cool down the room before you get home. —Mary H.J. Farrell (@mhjfarrell on Twitter) 8,000 BTU 115v Through-the-Wall Air Conditioner 10,000 BTU 115v Through-the-Wall Air Conditioner 10,000 BTU 230v Through-the-Wall Air Conditioner 10,000 BTU 230v Through-the-Wall Air Conditioner with Heat 12,000 BTU 115v Through-the-Wall Air Conditioner 12,000 BTU 230v Through-the-Wall Air Conditioner 12,000 BTU 230v Through-the-Wall Air Conditioner with Heat 9,800/10,000 BTU Cooling Thru-The-Wall Air Conditioner Cooling & Heating 11,200/11,500 BTU Thru-The-Wall Air Conditioner 10,900/11,200 BTU Cooling Thru-The-Wall Air Conditioner Cooling & Heating 8,000 BTU Thru-The-Wall Air Conditioner 9,800 BTU Thru-The-Wall Air Conditioner 10,000 BTU Thru-The-Wall Air Conditioner

11,500 BTU Thru-The-Wall Air Conditioner Designed to be built into the wall, these GE Air Conditioners do not have the side or top vents that are typical for window air conditioners. Built-in units offer a better weather barrier than standard window air conditioners and keep windows free of obstructions. Built-In Wall Air Conditioners Window AC units are portable, and are not installed into the structure of the home or building. GE window air conditioners are designed to fit traditional-style windows and come with our EZ-mount installation. Measure the square footage of the room or rooms to be cooled. If an exact match of cooling capacity is not possible, it is preferable to select a unit which is slightly undersize in BTUs, rather than oversize. If the area to be cooled includes a kitchen, add an additional 4000 BTU/hr. When sizing larger living areas, it is usually better to use at least two air conditioners rather than one large unit. Doing so offers better air distribution which reduces the likelihood of hot and cold spots.