Energy Consumption of Portable Air Conditioners Vs. Window Air Conditioners

Measurements

• The energy efficiency ratio and the British Thermal Unit are two measurements you need to know when shopping for an air conditioner. The EER measures an air conditioner's efficiency, specifically the ratio of the cooling capacity to the watts. The more efficient the air conditioner is, the higher the EER. The BTU measures thermal energy. In air conditioners, the BTUs measure the thermal energy the unit can remove from an area. The higher the BTUs, the more powerful the air conditioner.

Selection

• When purchasing an air conditioner of either type, look for an EER of at least 10. The federal minimum EER is 8 to 9.8. To calculate the BTU rating needed, figure that the average space needs 20 BTUs per square foot to cool with a window air conditioner. The portable air conditioners require about 20 percent more BTUs than a window air conditioner to cool a space.

Energy Use

• Most portable air conditioners use about 1,100 watts per hour. Divide the watts by 1,000 to get the kilowatts per hour. In this case, the kWh/hr used by the unit is 1.1. Multiply this by the cost of 10 cents per kWh and the unit costs $.11 per hour. As a comparison, most mid-size window units use 900 watts. To get the best energy comparison when shopping, figure out how many BTUs you need. Then choose the air conditioner with the highest EER. The unit with the higher EER will use the fewest watts. Appliances have a plate on the unit that gives the watts.

Energy Star

• Look for an air conditioner that has the Energy Star seal when purchasing a window unit. The Energy Star program tells you which units have met strict energy guidelines set by the Environmental Protection Agency. At the time of publication, Energy Star labels only window units. There are no federal standards that apply to portable units. The EPA considers portable units a short-term solution for home cooling.