According to the U.S. Department of Energy, the wattage of most appliances is stamped on the bottom or back of the appliance or possibly its nameplate. Wattage listed is the maximum power drawn by the appliance. However, the amount of power actually consumed varies with the setting being used. The Department of Energy also notes that if wattage is not found on the appliance, it can be estimated.
The estimate can be figured by finding the current draw in amperes and multiplying that by the voltage used. The majority of appliances in the United States measure about 120 volts, with higher-power appliances, such as dryers and electric stoves, using approximately 240 volts. An electric dryer has an approximate wattage of 4,000.
The government states that even when appliances are turned off, many use a small amount of stand-by power. These appliances include stereos, computers or TVs. Common household items and their wattage are as follows: laptop (50), vacuum cleaner (1,000 to 1,440), water heater (4,500 to 5,500), coffee maker (900 to 1,200) and microwave (600 to 1,500). An appliance using between 300 and 800 volts could be powered by solar power; one example of an appliance fitting this description is a refrigerator. To figure the estimated cost of running an appliance annually, multiply the annual consumption in kilowatt hour (kWh) by the utility company's rate per kWh consumed.