Importance of Watts for Appliances

Watts

• Appliances and other electrically powered devices convert electricity to different kinds of energy, such as heat or motion. For example, light bulbs convert electricity to light and stoves convert electricity to heat. The rate at which any device consumes electricity to make this change is measured in watts (W), actually a measurement of what physicists call "work." Most electric devices, including appliances, have a label that shows how much power in watts they use while running.

Kilowatt-Hours

• Electricity charges are based on how many kilowatt-hours (kWh) your household consumes in a month. This measurement might sound complex, but it's simple to break down. First, the prefix "kilo" means a thousand, so a kilowatt is 1,000 watts. One kilowatt-hour is an amount of energy equivalent to using 1,000 watts for one hour, whether from running a 1,000-watt heater for one hour or a 100-watt light bulb for 10 hours. To determine power usage in kWh, multiply the device's power needs in watts by the time it is used in hours and divide by 1,000.

Cost of Electricity Used by Appliances

• Appliances are significant power users. According to the U. S. Department of Energy, a medium-sized refrigerator uses 725 watts. Since the refrigerator runs 24 hours per day, that 725W means that it uses 17.4 kWh every day (725W * 24 hour / 1,000 = 17.4 kWh), and more than 6,300 kWh each year. Appliances that use less power, or fewer watts, than competing products save money on the owner's electricity bill. To help consumers determine potential savings, new appliances have bright yellow Energy Star labels that estimate how much it would cost to run them each year at an average electricity cost.

Appliances, Fuses and Circuit Breakers

• Homes are equipped with fuses or circuit breakers to limit the current passing through the wiring. These devices are designed to fail when the current is too high, resulting in a "blown" fuse or "tripped" circuit breaker. The maximum current allowed by fuses and breakers is rated in amps. The amps in a circuit equal the total wattage drawn by everything on the circuit divided by the voltage (120V in North America). For example, a 120V circuit with appliances totaling 2,000W is drawing a current of 16.67 amps (2,000W / 120V) when everything is running. If that circuit runs through a 15-amp fuse, the fuse would blow. You can reduce chances of blown fuses and tripped breakers by calculating the amps drawn by a circuit. Start by adding the wattage of all appliances, gadgets and electronics and divide that number by the voltage. For a 120V circuit, the total for all devices running at once should be less than 1,800W (a 15-amp fuse) or 2,400W (a 20-amp fuse or breaker). If you are getting close to the limit, it would not be wise to add new devices to the circuit.