How To Keep Cool When It’s Hot Outside

  • Close doors, windows and window coverings during the day when you’re out of the house, especially on the east and west sides. If safe to do so, open at night or in the morning to let in cooler air.
  • Avoid producing heat inside your home when it’s hot outside. Do laundry, run dishwasher, etc., in the early morning and late evening hours.
  • Try cooling down with a cold shower rather than cooling the entire house.
  • Consider installing an attic fan to draw hot air out of the house.
  • Plant deciduous trees or install awnings to shade your home, especially on the south and west sides of your house. Before planting trees, make sure they won’t interfere with power lines once they grow to their full size. Refer to our Tree Planning Guide for more information.
  • Consider installing a ceiling fan in rooms used frequently. Moving air can feel up to four degrees cooler than still air. Ceiling fans are effective in homes both with and without air conditioning.
  • Turn the air conditioner off when you’re going to be gone for an extended period.

Central Air Conditioning

Selecting and Installing Central Air Conditioning

  • If you are experiencing ongoing expensive repairs to your central air conditioner or if it is more than 15-20 years old, consider buying a new one. A new higher-efficiency unit, when properly sized and installed, will cost less to operate on a monthly basis.
  • Look for an air conditioner that has a Seasonal Energy Efficiency Rating (SEER) above 13 and has the ENERGY STAR® label. ENERGY STAR certified air conditioners are 25 percent more efficient than conventional units.
  • Buying the correct size unit and having it installed properly is critical to efficiency and comfort. Central air conditioners must be sized, installed, and set up by a licensed HVAC contractor.
  • Consider purchasing an air conditioner with variable speed motors for the outdoor fan and compressor as well as the indoor air handler. These variable capacity air conditioners are the most efficient available and can also provide increased comfort and less noise.
  • Ask a professional to inspect your duct system. Leaky duct systems are more common than you might realize and reduce the effectiveness of your central air conditioner and heating system.

Air Conditioner Maintenance

  • Routinely check your air conditioner’s air handler or furnace filter during the cooling season. Clean or replace as needed. Dirty filters block normal airflow and significantly reduce a system’s efficiency.
  • If you are experiencing a problem, have your air conditioner professionally serviced. Ask for a tune-up that includes a check of the refrigerant charge, cleaning of the coils and an inspection of your duct system.

Everyday Air Conditioner Tips

  • Don’t crank the temperature down in an effort to cool your house off quickly. It will not affect the speed at which the house cools.
  • Check your thermostat setting. Most people can be comfortable at between 74-78 degrees. Remember that thermostats are not always accurate.
  • Consider installing a programmable thermostat to allow for higher temperatures at night and when you are away without sacrificing comfort when you need it. Look for the ENERGY STAR label when shopping for programmable thermostats.
  • Weather strip doors and windows to prevent losing cool air to the outside.
  • Make sure there’s sufficient insulation throughout your home to help keep the heat out.

Window Room Air Conditioner

Selecting and Installing Window Room Air Conditioners

  • Shop for a unit with an energy efficiency ratings. Look for units with a high Energy Efficiency Ration (EER), high Combined Energy Efficiency Ration (CEER), or high Seasonal Energy Efficiency Ration (SEER). Better yet, buy an ENERGY STAR certified unit, which has a designated CEER based on its cooling potential. ENERGY STAR certified window room air conditioners use at least 10 percent less energy than models built to current minimum-mandated efficiencies and significantly less than older models.
  • Install the unit in a north window or shaded area for optimal operation.
  • Consider a unit with controls such as a digital readout for the thermostat setting and a built-in timer, both of which can help you adjust your unit to use less energy.
  • Bigger is not always better! Purchasing a unit that is too large is actually less efficient. Use this chart to determine what size you need. For room AC units, size is measured in BTUs, an indication of cooling capacity.
Area To Be Cooled
(square feet)
Capacity Needed
(BTUs per hour)
100 to 150 5,000
150 to 250 6,000
250 to 300 7,000
300 to 350 8,000
350 to 400 9,000
400 to 450 10,000
450 to 550 12,000
500 to 700 14,000
700 to 1,000 18,000

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 per person.
  • If the unit is used in a kitchen, increase capacity by 4,000 BTUs.

Window Room Air Conditioner Maintenance

  • Clean filter monthly when in use. Wash foam filters with soap and water and air dry.
  • Vacuum the coil fins.

Everyday Window Room Air Conditioner Tips

  • Install a timer on the unit if you want the room cool when you get home. Make sure the timer is rated for the amperage and voltage of your window room air conditioner.

Ceiling Fans

Selecting and Installing a Ceiling Fan

  • ENERGY STAR certified ceiling fan/light combination units are 60 percent more efficient than conventional fan/light units. Savings come mostly from the lighting on the fan so, if your fan doesn’t include lighting, be sure to purchase an ENERGY STAR certified light kit.
  • For summer and winter savings, buy a reversible fan that will create a down-draft in summer and reverse to circulate warmer air near the ceiling in winter.
  • Install the fan with the blades at least seven feet above the floor, one foot below the ceiling and two feet from the nearest wall.
  • Consider the size of the room and the size of the blades when selecting a ceiling fan. Multiple fans may be needed in rooms longer than 18 feet.

Everyday Tips for Ceiling Fans

  • Switch the fan and light off when you leave the room. Fans don’t actually cool a room — they cool people. When circulating air passes over your skin, it picks up evaporating moisture making you feel up to 4 degrees cooler.
  • If your ceiling fan has a reversible motor, reverse the fan during the winter months to push warm air up toward the ceiling and circulate it throughout the room.

Evaporative Cooler (also called Swamp Cooler)

Selecting and Installing an Evaporative Cooler

  • Select a unit that has two or three blower speeds and a thermostat that automatically turns the cooler on and off.
  • Sizing an evaporative cooler is less critical than sizing an air conditioner. The suggested guideline is about 3 cubic feet per minute (CFM) of airflow per square foot of area to be cooled.
  • Place your evaporative cooler in a place free of outdoor obstructions, vents or combustion appliances. Make sure you can plumb a water supply pipe to it.

Evaporative Cooler Maintenance

  • It is helpful to have your cooler serviced twice a year — once before the cooling season and once during the summer.
  • Have the unit winterized professionally before the winter season.

Everyday Tips for Your Evaporative Cooler

  • Expect outdoor air to be cooled about 15-20 degrees using an evaporative cooler. The lower the humidity, the more effective the cooling is. Cooled air from an evaporative cooler will add humidity to your home.
  • Leave at least one window open while operating an evaporative cooler. The cooler air will go to the rooms with airflow and push the existing air via convection to the outside, so open doors and windows accordingly.
  • During moderate temperatures (less than 85 degrees), use just the evaporative cooler fan to draw cooler outdoor air into the home without using the cooling media to cool the air.
  • Expect to use about one third of the electricity needed to operate an air conditioner of similar capacity. At the same time, however, your cooler will use anywhere from 3 to 15 gallons of water per day.

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