Two major decisions should guide your purchase of a room air conditioner. Buy a correctly sized unit. Buy an energy-efficient unit. If the room is very sunny, increase capacity by 10%. If the unit is for a kitchen, increase the capacity by 4,000 Btu per hour.
Air conditioners need room to take in and exhaust air and should have at least 18 inches of clearance from furniture, plants, and drapes. If the air cannot circulate around the unit, heat may build up and cause damage to the coils.
If you have a room air conditioner, remove it for the winter or seal it up and insulate it. Water heater insulation jackets can work well for covering and insulating the air conditioner.
If your house is for sale in summer, run the air conditioner. If it's 90 degrees inside, buyers will pay more attention to the temperature than to the attractive features of the house.
Turn the air conditioner thermostat up to at least 78° or higher or use a programmable thermostat. Close doors to unused rooms. Turn air conditioners off when no one is home.
Set your thermostat as high as comfortably possible in the summer. The less difference between the indoor and outdoor temperatures, the lower your overall cooling bill will be.
Run your air conditioner for a few minutes in the spring, before you need it. If you wait until the first hot day to discover is isn't working, you'll find yourself on a waiting list, sweltering sometimes for days before an air conditioning specialist can come to fix it.
Don't set your thermostat at a colder setting than normal when you turn on your air conditioner. It will not cool your home any faster and could result in excessive cooling and, therefore, unnecessary expense.
Change the filters regularly. Dirty filters restrict air flow, reducing efficiency and worse case, can cause the evaporator to ice up. Disposable fiberglass filters should replaced. Electrostatic or electronic filters need to be washed regularly.
Set the fan speed on high except in very humid weather. When it's humid, set the fan speed on low. You'll get better cooling, and slower air movement through the cooling equipment allows it to remove more moisture from the air, resulting in greater comfort.