Room Air Conditioner Efficiency, Use and Maintenance Tips

Tips on Cooling Capacity: How many BTUs do I need?

It is extremely important to choose a room air conditioner of proper cooling capacity. A unit with too much cooling capacity will be inefficient and expensive to operate. A unit that’s too small won’t do a satisfactory job. To determine the best sized air conditioner for your room, click here  for our room calculator worksheet.

There is also a close relationship between cooling capacity and dehumidifying the air. An oversized unit will quickly cool the air without remaining in operation long enough to dehumidify it, and a “cold, clammy” feeling will result.

After determining the size unit needed, consider its operating efficiency. An efficient room air conditioner uses less electricity, so it costs less to operate.

To measure efficiency, engineers have established a room air conditioner Energy Efficiency Ratio (EER). It is computed by dividing Btu/h (cooling output) by the watts of power (electrical input) in accordance with U.S. Department of Energy Test Procedures. Federal Trade Commission regulations require that this value be placed on the label attached to the product. Thus, a 12,000 Btu/h model might use 1,900 watts and have an EER of 6.3, while another model of the same capacity might use 1,350 watts and have an EER of 8.8. The higher EER is the more efficient of the two. AHAM’s searchable directory lists EER’s for all units.

Tips for Installation

Before installing room air conditioners, check your home wiring for the right circuit amperage and voltage. Avoid lines already loaded with appliances. Do not connect a 208-V unit to a 115-V line or a 115-V unit to higher lines. If a fuse blows, shut off the unit and check load and wiring. Be sure the outlet is properly grounded. Never remove the grounding prong from the plug. Install the unit in a shaded window, if possible. Keep warm air out by weather stripping doors and windows and keeping them tightly closed. Close fireplace dampers and seal openings to the attic or other uncooled areas. Seek professional advice on recommended ceiling and wall insulation.

Tips for Energy Efficiency and Maintenance

  • Turn off the unit and open doors and windows during cooler periods.
  • Use the unit fan and portable fans to draw in cooler outside air and increase circulation. 
  • Although air conditioners also dehumidify, a dehumidifier in the basement can prevent excess moisture seepage through the house. 
  • Use a higher (warmer) thermostat setting during peak periods or when the area is unoccupied. A setting of 75 to 80 degrees will cut power consumption by 15 percent. 
  • Don’t let heat build up all day and then try to cool areas quickly by turning the controls to maximum settings. Start units earlier in the day and cool areas slowly before they are occupied. 
  • Avoid activities that generate high heat and humidity (i.e., cooking, bathing and laundering) during high heat hours. 
  • Draw the shade or window blinds to reduce solar and outdoor heat. Reflecting and double-pane glass, awnings, overhangs, louvered sunscreens, plantings, fences or adjoining buildings also help ─ but be sure not to block the back of the unit. 
  • Regularly change or clean filters, and check air flow for blockage and evaporator coil for frost. 
  • Use a vacuum cleaner attachment to clean accessible parts but be careful not to damage them. 
  • Have the unit checked and cleaned at the start of the season. During the off season, make certain it is cleaned and properly covered and disconnected.