Informational Guide

Window AC Guide

Read our quick & easy guide to the best window air conditioners. Learn how much cooling power you need & what type of AC unit is suitable for your room.

by Josh M

A hot day in a building without central air conditioning can get unbearable. Fans don’t help much, and most solutions seem very complicated and even more expensive, but neither you nor your wallet really need to suffer under the relentless summer heat.

Window air conditioners let you cool specific rooms, rather than your whole house, apartment or business space. It takes less energy to cool only the rooms that need cooling, than running a central air conditioner unit. This is an easy way to reduce your electricity usage.

A window air conditioner is a perfect choice if you want to cool a specific room, or a few specific rooms, and spend less on cooling costs. With adjustable thermostats, timers, and in some cases even Smartphone controls, these cooling units help you get the temperature you want. When you want it! Without wasting energy to keep the rooms cool at all times.

Find out if a window air conditioner unit is the right choice for you by looking at these pros and cons.

    • The popularity of window AC makes them easy to find and competition keeps the prices down
    • Relatively quiet and efficient
    • Drains water automatically
    • Fits in windows and wall holes
    • Rooms up to 300 square feet can be cooled even with small units. Larger ones work for rooms up to 650 square feet
    • With clever placement, it’s possible to cool more than one room

Window AC Disadvantages

    • The unit blocks an entire window when installed
    • Water dripping from the unit outside the window can land in inconvenient places (for example, on people)
    • Some windows are the wrong size for these units or otherwise can’t support them
    • Can be difficult to remove once installed
    • The included panels may let hot air through, reducing the unit’s efficiency.

Choosing the Right Window Air Conditioner

Finding the right window air conditioner for your needs is crucial and can make a big difference in both energy cost and comfort. Here are the key factors to look for.

Getting the size right is important. Units that are too small will have a hard time keeping the temperature down. Overly big ones, on the other hand, will be inefficient. Not only is it wasteful, the rapid cooling also means higher humidity, making the room feel moist and “clammy.”

Air conditioners typically need about 20 BTUs (British Thermal Units) per square foot. The typical cooling capacity of window air conditioners ranges between 5,000 and 14,000 BTUs per hour. Note that the size and weight of the unit increase with the cooling capacity.

Air conditioner energy efficiency is measured as EER (energy efficiency ratio). EER measures the ratio of cooling capacity (in BTu per hour) to power input (in watts). A higher EER rating means a more efficient air conditioner. An additional 1.0 of EER means 10% more efficiency, and lower operating costs. You can find information about a unit’s EER on the EnergyGuide label of the air conditioner.

Newer air conditioners cost less to operate due to higher energy standards in recent years. An EER of at least 12 is recommended. Keep an eye out for the ENERGY STAR label, which marks products that meet the strict guidelines for energy efficiency set by the U.S. Department of Energy and the Environmental Protection Agency.

Remember, higher EER means lower operating costs. On top of this, newer units conserve energy by shutting down when the room reaches the right temperature and starting again when it gets warmer, while older types keep the fan running and using electricity.

[Window air conditioner energy saving tips]

The unit must also fit your window. Carefully measure the inside dimensions, and keep in mind that the majority of window air conditioners are built for double-hung windows with a sash that can be raised or lowered.

Make sure that your electrical system meets the air conditioner’s requirements. Smaller units that draw less than 7.5 amperes work fine on any household electrical circuit, granted no other major appliances share the circuit. Larger units require their own 115v circuit, and the biggest ones need a dedicated 230v circuit.

Other Features to Consider

  • A programmable timer, to turn the unit on when it’s needed and off when it’s not, thus conserving energy and money.
  • Dehumidification capabilities differ between different models. You can find a rating, in pints and ounces per hour, of dehumidification.
  • Mechanical controls to let you adjust cooling level and fan speed.
  • Electronic controls let you set a target temperature for the unit to maintain.
  • An electronic ionizer makes the air conditioner better at reducing dust, pollen, and other air impurities.
  • remote control with a temperature sensor lets you set the air conditioner to activate when the temperature around the remote rises above the one you’ve specified.
  • Smartphone control allows you to turn the unit on or off and adjust settings from afar, so you can always come home to a cool room without running your air conditioner at all times. This is perfect if your schedule is irregular.
  • A removable filter makes it easy to keep the unit clean and at optimal capacity.
  • Filter alerts notify you when it’s time to clean the filter. Dirty filters make the unit use more energy for lesser results and may shorten its lifespan.
  • With an extra-long cord, it’s easier to reach a suitable power outlet.
  • Functions like “Turbo” and “Power thrust” help to push the cool air farther into long, narrow rooms.

Room Examples and Recommendations

Bedroom (100 – 300 square feet)

For a small or medium size bedroom, you will need a unit with a capacity between 5,000 and 6,500 BTu/hr, and a low noise rating. Some units feature a sleep setting, which reduces noise and energy usage by running the fan less frequently to avoid excess cooling when you sleep.

Living Room (350 – 650 square feet)

A living room calls for a larger air conditioner. There’s more open space and it takes more to cool rooms that often contain more than two people. An extra 600 BTu/hr per additional person is recommended. This means you’ll want a capacity of around 9,800 to 12,500 Btu/hr.

Kitchen (150-250 square feet)

Kitchens can vary a lot in size and shape, but they tend to need quite strong units. An extra 4,000 BTu is recommended for a unit used in a kitchen, to compensate for the heat generated by the stove and other hot appliances. You’ll want a unit with a capacity in the range of 7000 to 9000 BTu/hr.

If you’re confused about the size of your room or your cooling needs, take a look at this cheat sheet and calculator for window AC capacity needs.

Energy Efficiency of Room Air Conditioners

You can increase efficiency and comfort, and reduce energy costs, by ensuring optimal conditions for the air conditioner.

With proper placement and regular maintenance, the unit will perform better. Follow these directions to get the most out of your air conditioner.

  • A window in the shade is optimal, increasing efficiency by up to 20% compared to a sunny window. Windows facing north get the most shade.
  • The unit must be level to ensure proper function.
  • Make sure that nothing blocks the unit’s airflow.
  • High fan speeds are generally best, but on really humid days the slower settings are better for keeping humidity down.
  • Keep lamps, TVs, and computers away from your air conditioner. It will run longer than necessary if its thermostat senses heat from hot electronics.
  • Consider using an interior fan in conjunction with your window air conditioner to spread the cooled air through your home without greatly increasing electricity use.
  • Get help when installing. Window air conditioners are quite heavy.
  • Basic maintenance helps retain maximum efficiency its lifespan. Here’s how to do it.
  • Optimal efficiency relies on proper air sealing and insulation. Energy Star recommends the following adjustments.

Following these tips and guidelines will help you find the perfect window air conditioner for your needs and keep your cool without paying too much. To learn more about cooling options in your home, check our favorite small portable ACs and quietest portable ACs.