A low-wattage air conditioning unit is cheaper to use than more powerful air conditioners or central air systems if it is sufficiently powerful to cool a room, as reported by finance website DailyFinance. In addition, low-wattage air conditioners are often less expensive to purchase than more powerful units as well.
A low-wattage air conditioner is cheaper to run than a more power-hungry cooling solution on a per-minute basis. However, low-wattage air conditioners that are insufficiently powerful to cool an area often run for a longer period than an air conditioner with higher power consumption that is sufficiently powerful to cool the area in question. This leads to higher overall power consumption from the low-wattage unit and higher costs. To avoid this outcome, DailyFinance recommends using an air conditioner rated to remove 20 British thermal units of heat per square foot of space in the area where the unit is intended for use. For example, a 200 square foot room requires an air conditioner rated to remove 4,000 BTUs of heat for adequate cooling.
An air conditioner's efficiency rating also affects its overall energy usage and cost to operate. An air conditioner that is rated with an Energy Efficiency Rating of 10 by the Environmental Protection Agency cuts energy usage in half versus a unit of the same wattage with a an efficiency rating of five.