buying guide air conditioners

keep your cool.

Cool comfort is possible on hot days thanks to air conditioners. But did you know they also
remove humidity and most impurities? Air conditioners are one of the most energy-efficient
ways to cool your home.

know your cooling needs.

  • room size

  • Finding the right-size air conditioner can be a bit of a Goldilocks game: too small and it won't work effectively; too large and the room is cooled too quickly, leaving clammy-feeling moisture in the air.

  • energy efficiency

  • The Energy Star rating or Energy Efficiency Ratio (EER) appears on the yellow Energy Guide label on the air conditioner packaging. Ratings range from 8–11.5. The higher the EER, the more efficient the unit—and often the more expensive. But it will save money by cooling efficiently. If you're in a hot climate, consider a rating of 10 or higher.

  • how big an air conditioner do you need?

  • These tips from ENERGY STAR will help you calculate the ideal-size air conditioner for your room.

  • find the right size
  • installation location

  • If the air conditioner cannot be centered on the wall, look for a unit with an adjustable airflow so the air can be redirected. If possible, place the unit in a shaded window for added cooling efficiency.

  • Btu explained.

  • For air conditioners, a Btu measures the amount of heat an air conditioning unit can remove from the room. As the Btu rating increases, so do the size, weight and cost of the unit. Matching Btu requirements to room size is important for the unit to work efficiently. For example, if placing your air conditioner in a sunny location, increase Btus by 10%, and for shady locations decrease by 10%.

air conditioners by room size.

  • large-room air conditioners.

  • Large-room A/Cs are great for big rooms between 400–700 sq. ft., and their capacities range from 10,000–14,000 Btus. Take note of their bulk and weight, though, which can make them awkward and difficult to install.

  • mid-sized-room air conditioners.

  • Mid-sized-room A/Cs tend to be more expensive, and their size and weight make them more difficult to install and remove. These A/Cs have capacities that range from 8,000–9,000 Btu/hour, and they work well in mid-sized rooms between 300–400 sq. ft.

  • small-room air conditioners.

  • The lightest and least expensive units, small air conditioners' capacities range from 5,000–7,000 Btu/hour. Btu = The air conditioner's cooling capacity (Btu per hour). A small-room air conditioner is ideal for rooms between 100–300 sq. ft.

air conditioner by type.

  • portable units.

  • These units cool a specific area, not an entire home, and often are on casters for mobility. A flexible hose attaches to a window to exhaust hot air. You may need to empty a water reservoir, but some come with a drainage hose. In general, these are easy to set up and relocate, but can be heavy and less efficient.

  • window units.

  • Be sure to measure your inside window dimensions before you shop. Accordion panels—often included—help achieve a secure fit, and weather stripping can help, too. In general, window units are easy to install, remove and store. They're also affordable, especially when they offer both heating and cooling features. The biggest disadvantage is that they block the window where they're installed.

  • built-in wall units.

  • Intended for permanent operation, these often provide both cold and hot air features. A hole in an exterior wall is required for ventilation. In general, built-in units are great because they don't take up window space or rely on an airtight fit. They also often have a wireless thermostat option. These units are usually more expensive, though, and can require a more involved installation or additional parts.

Fahrenheit-dropping features.

Look for these frigid-air features to make your life a breeze.

  • timer & programmable thermostat.
  • Keep your home cool without continuously running the A/C. A heat-sensing thermostat senses the air temperature of the room and adjusts the temperature of the air coming from the unit.

  • remote & digital controls.
  • Conveniently adjust temperature from anywhere in the room with a remote control. Some digital controls let you specify an exact temperature, and large LED displays make using this feature easy.

  • fans & adjustable airflow.
  • Combined with a programmable thermostat, a variable-speed fan makes any A/C an effective room cooler. Additionally, adjustable airflow settings—most units have 2–3 speeds—provide comfort control. Movable fins allow air to be directed where needed. Some units let you choose between fresh and recirculated air.

  • sleep & energy-saving settings.
  • This feature allows the unit to operate on a very low setting, which saves energy while making the room comfortable for sleeping.

  • air purifier & dehumidifier.
  • A dehumidifier can be useful in damp climates or in extremely hot and humid weather, while an air purifier can clean air of allergens and some germs. Some units also include a heating function.

installation & maintenance.

Check out this information to help you stay safe and keep your A/C running efficiently.

installation tips.

Follow the manufacturer's instructions for safe and proper installation. Because units can be heavy and bulky, ask for help to avoid injury. Be cautious when installing units in high windows, and always follow the electrical guidelines.

electrical requirements

Some electrical issues to consider include: How far is the outlet from the window? What's the room's available amperage? Be sure that you use an outlet designed to accommodate an A/C unit's amps. 208/230-volt models require one of three branch circuit power supplies (see graphic).

  • Parallel 115V. 15 Amp.
  • Tandem 230/20 15Amp.
  • Perpendicular 230/208V. 20 Amp.

care & maintenance tips.

keep it clean

Always unplug the unit before performing any maintenance or cleaning. Most problems can be avoided with routine maintenance: clean and replace the filter and coil per the manufacturer's instructions to increase efficiency, and periodically clean the entire unit for peak performance.

older units

With older units, remove the inside grille and take out the foam filter. Wash the filter in soapy water until clean, then rinse it and let it dry. Very old or dirty filters can be inexpensively replaced.

window units

Vacuum inside window units to remove dirt and debris. Cover electrical components with plastic, then wipe inside the unit with a damp cloth. Clean and repair the window and sill if needed. When all parts are dry, replace components, put the unit back in its window location and reseal with new weather stripping.