What the best portable air conditioner has

  • Energy efficiency. The energy efficiency rating (EER) is a measurement of how much energy it takes to run an air conditioner in relation to its cooling capacity. A higher number indicates a more efficient unit, which can save money on the monthly electric bill. Portable air conditioners commonly have an EER of 10.0 or above, but the best rate is 11.0 or higher.
  • Environmentally friendly refrigerant. Most new air conditioners use R-410A to stay cool, which is better for the atmosphere than the older R-22 refrigerant. In addition, users with an R-22 air conditioner will have a difficult time when they need to recharge their units. As manufacturers transition to R-410A only, R-22 is becoming less available and more expensive.
  • Low fan noise. A loud compressor is one of the most common air conditioner complaints -- owners want to be able to stay cool while comfortably watching TV or sleeping. The best portable air conditioners create a white-noise sound that's 50 decibels or less.
  • User-friendly controls. Portable air conditioners with a digital display are the easiest to read and set, though the display shouldn't be glaring enough to be disruptive in the dark. A remote control offers limited functions, but can be extremely convenient in bedrooms and large living rooms.
  • Dehumidifier. While all portable air conditioners remove a certain amount of moisture from the air, the best feature is a separate dehumidifying function. This reduces the humidity in your room without adding an icy blast, a handy setting for muggy days that aren't hot enough for air conditioning.
  • Easy to move. Part of the convenience of a portable air conditioner is that it can be rolled when installing and storing. The best units have easy-rolling caster wheels and are light enough to be manageable. Compact designs also help save space.
  • Warranty. The best portable air conditioner brands cover the compressor for at least three years, but it's important to read the fine print: Some brands require owners to front the cost of shipping the unit for warranty service.

Know before you go

Where will the air conditioner go? Select the size of portable air conditioner based on the square footage and setting of your space. The ideal size has enough power to effectively cool your room while running long enough to remove as much moisture from the air as possible. An air conditioner's cooling capacity is measured in Btu (short for British Thermal Unit) -- the higher the number, the more powerful the unit.

  • 10,000 Btu and smaller: A small portable air conditioner, also called a mini air conditioner, is best for 300-square-foot rooms and smaller. This is a good pick for bedrooms and living spaces in small apartments.
  • 11,000 Btu and larger: Large portable air conditioners with a cooling capacity of 11,000 Btu and above work well for rooms over 300 square feet, such as living rooms. Rooms with extra heat sources need more help staying cool; for most rooms with full sun, an air conditioner that is at least 11,000 Btu is best. Kitchens typically require at least 12,000 Btu to stay cool.

A window is still required. Air conditioners need outside air to function at their best, and a portable unit is no different. Each comes with a window kit, which uses a few inches of window space for a vent hose. Appliance experts say one of the most common complaints about poor performance results from improper venting or incorrectly installing the window kit. Most also prefer dual-hose units -- especially for large rooms -- saying that they provide extra cooling power with a more stable air pressure. One hose circulates the inside air while the second uses outside air only to keep itself from overheating. With a single-hose design, on the other hand, the air conditioner has to work even harder to lower the temperature in your room.

Will you need to empty the water tank? Air conditioners pull extra moisture out of the air -- reducing your room's humidity and making it more comfortable. The best units use a self-evaporative system to automatically disperse this moisture out of the vent hose. For units without this system or excessively humid regions, users have to manually drain the water tank or install a drain hose.

Filtering the air. Some portable air conditioners include one or two built-in air filters. For maximum filtration, look for a unit that has a washable pre-filter and an additional carbon filter, which can remove finer particles such as mold, pollen and dust. Determine the life span and replacement price of the carbon filter to better understand your maintenance costs.

Check your outlets. A portable air conditioner can pull a lot of power; make sure your outlets can manage the extra load, and never use an extension cord.

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