The average home uses more electricity for cooling than for any other appliance or accessory, if you want to save money on your utility bill, carefully consider your cooling choices. A central air unit uses more energy to cool your home. A window unit uses anywhere from 500 to 1440 watts to run, while a 2.5 ton central unit (about the size for a typical 1,500- to 2,000-square-foot home) uses about 3,500 watts.
Keep in mind that window units aren’t necessarily more energy efficient than central air units. A window unit that is too small to cool a room may run continuously, wasting energy. Central air units cool multiple rooms more quickly and filter out airborne particles — but they also use more power than window units. When you’re shopping for a central air conditioning system, make sure the SEER number (seasonal energy efficiency ratio) is 13 or better (14 in warmer climates). A less efficient system will cost you more to run.
Although it costs more to purchase and install a central unit , if you plan to cool three or more rooms, the most cost-effective and energy-efficient choice is the central unit. A central unit has greater resale value and humidity control. Also multiple window units typically use more energy than a single central unit. Consider that three rooms likely is a large portion of the home, and every time you travel between cooling zones with a window unit, you’re leaking cool air, making your unit work harder. However, neither Central or Window units will work efficiently and save money unless it is properly sized.