Determine how many kWh per day an appliance uses with this formula:
Wattage × Hours Used Per Day ÷ 1,000
You can find the wattage on the nameplate.
Or, just buy a watt meter like Kill A Watt.
In 1980, 27 percent of homes in the United States had central air conditioning; in 2001, that number jumped to 55 percent [source: EIA]. Air conditioning, which typically uses high-watt machines for extended periods of time, accounts for a big chunk of residential energy use.
As usual, the actual number of watts consumed in cooling a home varies greatly depending on the type of unit, the capacity, the time it's operating and the efficiency rating. An air-conditioning unit might use anywhere from 200 to 1,800 kWh/month. Here's a rough breakdown of what different AC devices use:
- Window unit: 200-650 kWh per month [source: MCEC]
- Heat pump: 600-1,800 kWh/month [source: MCEC]
- Central air: 300-900 kWh per month [source: CPPD]
You can take some important steps to improve the efficiency of an air conditioner, including:
- Have a pro check the unit every year. Proper fluid levels, coolant charge and insulation are crucial to keep the device working efficiently.
- Close the vents in rooms you hardly ever use.
- Upgrade to a timed thermostat that will automatically switch off the AC as the temperature outside gets cooler.
- Make sure you have at least 16 inches (41 centimeters) of insulation in your attic. This will keep more of the sun's heat out of your living space so the AC doesn't have to work as hard.
- [source: ATF]
You can also upgrade to a more efficient model or, on the other end of the spectrum, decide a little sweat might not be so bad for you after all.
Up next: More warmth, more watts.