Complete Guideto Buying an
Air Conditioner

In case you hadn’t noticed, summer heat waves are feeling a little hotter, lasting a little longer and coming a little more frequently. Whether you live in a part of the country known for sweltering heat or just find that a fan doesn’t provide enough relief, here’s a guide to buying a new air conditioner. Just in case you might be looking for an excuse to trade in your old AC unit, there’s a good chance a newer model is quieter and more energy efficient than your old unit.

Complete guide to buying a Air Conditioner
Features that matter
Getting the Right Size Air Conditioner is Most Important Getting the Right Size Air Conditioner is
Most Important

Getting the right size air conditioner for the space and climate is probably the most important consideration. Here are some reasons why using an oversized air conditioner is a bad idea:

  • Cycling on and off frequently (called "short-cycle") is not as efficient for air conditioners and can also increase electricity bills.
  • Oversized units may not run long enough for moisture to condense on the coils and dehumidify the air which can create a good environment for mold and mildew.
  • They can leave a room feeling cold and clammy.
  • Short-cycling creates more wear and tear on the compressor which can shorten the life of the unit.
  • Oversized units can also be noisier than smaller ones.

If your current unit constantly turns on and off over short periods or If the compressor runs for less than 5 minutes at a time, there’s a good chance it is oversized for the room you are trying to cool.

Undersized air conditioners will not be able to cool your room on a very hot day and can increase your electric bill in the process of trying. On the upside, undersized air conditioners will still dehumidify the air which could be just what you want on a mild rainy day, and it will do it cheaper than a larger unit.

How to size an air conditioner

Cooling capacity is measured in British thermal units (BTUs). Here’s a chart to help you pick an air conditioner with the right capacity:

Area (Square Feet) Capacity (BTUs)*
100 up to 300 5,000 -7,000
300 up to 450 8,000 – 10,000
450 up to 700 12,000 – 14,000
700 up to 1,400 18,000 – 23,000
1,400 up to 2,500 24,000 – 34,000

*Adjustments to Capacity:

  • Reduce capacity by 10 percent for heavily shaded rooms
  • Increase capacity by 10 percent for sunny rooms
  • Add 600 BTUs for each additional person regularly occupying the room.
  • Increase capacity by 4,000 BTUs for a kitchen
  • Mini split air conditioners may require more capacity for room size.
Air Conditioner Basics Source: Wikimedia Air Conditioner Basics

Not including central air conditioners, which require lots of duct work but can heat your whole house, your choice for a room air conditioner will most likely include a window unit, a portable unit or a mini split air conditioner. There are plenty of air conditioners to choose from that use an environmentally-friendly refrigerant gas that is compressed and then expands to remove heat and water from the air.

Air Conditioner

Hot air from the air conditioner is vented outside either by placing the part of the unit that produces hot air outside like a window air conditioner. You can buy a window air conditioner for around $200 or a little more for a larger capacity unit. They are fairly easy to install although you have to make sure there aren’t a lot of air leaks around the unit which could cause the unit to work harder. Portable air conditioners don’t take up a whole window but usually require a vent tube or two to pass through a window. They can be moved around but removing the condensate water that collects can be an issue. Mini split air conditioners are very quiet and efficient but require one unit inside and another outside with some connections between them. They can cost over $1000 for the two units and usually require a professional installation which could cost another $500 or more. In less humid areas you might be able to get by with a swamp cooler which is less expensive and works by passing air over evaporating water to cool a room.

Shop For top rated air conditioners
These apps help size an Air Conditioner Use These Apps to Help Size an Air Conditioner

Although it’s not that difficult to get a sense of how many BTUs you’re going to require for the room you want to cool, there are some apps you can use to make it easy and fun. Panasonic offers an Android and iOS version of an app that was intended for the Australian market but can be used anywhere. Smug Mug Software offers a free Android app that gets good marks from users. Haier offers a selector app of their own for iOS.

Apps and Remote Control Apps and Remote Control

As apps become more integrated into household appliances like refrigerators and washing machines, it seems only natural that apps become part of an air conditioner “system.” Samsung lets you control their air conditioner with an iOS or Android device so you can make sure your room will be nice and cool by the time you get home. Friedrich offers a Wi-Fi adaptor for their Kuhl air conditioners that allow you to control it from your iOS device or Android device. LG also offers remote control of some of their air conditioners with an Android app.

Higher Energy Efficiency Ratio is Better Higher Energy Efficiency Ratio is Better

Air conditioners are rated on their energy efficiency with an EER (Energy Efficiency Ratio) rating which is the ratio of BTU cooling output per hour divided by total watt-hours of energy consumed. For example, a 10,000 BTU unit that uses a kW per hour would have an EER of 10. As of 1990 air conditioners have been required to have an EER of at least 8 but they need a rating of 10.8 or better to qualify for an Energy Star label. In addition to an EER you may see a “Seasonal” EER or SEER which takes into account climate differences and can be used to predict the cost of operating an air conditioner in your area. For example, a 14,000 BTU air conditioner with a SEER of 14 would use 1kW per hour which at a typical cost of electricity of around $.15/kWh would cost 15 cents an hour to run. SEERs must be at least 14 to get an Energy Star label. In general, the higher the EER or SEER, the better, but the price usually rises correspondingly which could offset the money you might otherwise save on electricity.

Inverter Technology Saves Energy Inverter Technology Saves Energy

Inverter circuitry has typically been used to change DC power, like the kind that comes from solar panels, to AC power, which is what most homes use. Some air conditioner manufacturers including Samsung, Sharp, Panasonic, Mitsubishi and others have started using inverters to adjust the power going to the compressor to allow the motor to run at variable speeds instead of the normal full-on or off mode in most air conditioners. The Mitsubishi Mr. Slim mini-split air conditioner uses an inverter to help it reach a SEER of 21. Inverter-based air conditioners have several advantages over conventional units including:

  • Reduced power consumption
  • More precise temperature control or less fluctuation in room temperature
  • Lower power surge when compressor motor turns on
  • Less wear and tear on compressor
  • Quieter operation
Air Conditioner Roundup
Portable Air Conditioners Portable Air Conditioners

Portable air conditioners have some advantages over window air conditioners; they don’t block a lot of the window and they can be moved from room to room however, Consumer Reports recommends a window unit over a portable. They also say if you are going to get one opt for a dual hose model which brings air in from the outside as well as venting hot air back out. The other drawback with portables is dealing with the condensate water that collects. Some units claim they can evaporate the water while others fill a bin that needs to be emptied. The Sharp CV-2P10SX 10,000-BTU portable air conditioner uses a single exhaust hose which claims to remove condensate as well as hot air. We’ve read that some Costco stores have been offering this Sharp, “Library Quiet” unit that purifies and dehumidifies air for around $350. The reviews on the Soleus PH3-12R-03 are mixed but this unit has a heat pump that can warm a room as well as cool it. The NewAir AC12000E 12,000-BTU portable air conditioner will cost you close to $500 but it gets good marks from users and offers a “self-evaporative condensate system,” that claims to eliminate the need to drain the condensate water.

Shop for top rated portable air conditioners
Window Air Conditioners Window Air Conditioners

Window air conditioners can be the least expensive and easiest to install and there are many to choose from. The Frigidaire FRA052XT7 5,000-BTU gets good marks for quiet operation and will cost you less than $200 but will only cool a relatively small room like a bedroom. For a few dollars more, you can move up to the highly rated 10,000-BTU Frigidaire FRA106CV1 or the 8,000-BTU LG LW8012ER which has a remote control but some users complain about the fan noise. The Friedrich Chill CP08G10 is not a window unit but rather is installed through a wall. It gets good marks for reliability and quietness.

Shop for top rated window air conditioners
Samsung AS24ESP Frigidaire FRS12PYS1 LG Mini Split Air Conditioner LS307HV
Mini Split Air Conditioners

Mini split air conditioners mount the cooling coils high on a wall of your house and run connections to the compressor unit outside. They cost quite a bit more than window air conditioners and usually require professional installation but offer many advantages including:

  • Much quieter indoors because compressor and its fan are outside the room
  • Quiet outdoor unit doesn’t disturb neighbors
  • Also quieter because fan inside the indoor unit runs continuously and slower
  • Lower airflow means more dehumidification
  • Many units offer anti-bacterial filters
  • Many units use inverter technology

Samsung offers a line of mini split air conditioners like the Samsung AS24ESP that offers inverter technology, precise temperature control and a silver coated filter to help eliminate dust particles, fungi and unpleasant odors. The 12,000-BTU Frigidaire FRS12PYS1 can cool a 500 square foot room, offers inverter technology and has a very good SEER of 18. The LG Mini Split Air Conditioner LS307HV is a large capacity, 30,000 BTU unit that uses inverter technology and can easily cool a 1500 square foot room.

Shop for top rated mini split air conditioners