Volts and watts are both units of measure you can use to determine how much electricity an appliance uses. Appliances in the U.S. typically use 110 to 120 volts, but their wattages vary more widely. By converting volts to watts, you can understand the relation between the two measurements and how they affect your daily life.
Not a Direct Conversion
Voltage is, simply put, the potential electricity available to an appliance. Wattage is the amount of energy the appliance uses. Though volts and watts are related, you can't convert directly from one unit to the other. You need more information.
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Required Information
Amperage is the missing part of the "volts to watts" equation. It's the electrical current that flows through the appliance, and you can find it by reading the packaging for the appliance or the appliance itself. You can find the appliance's voltage the same way.
Calculation
Calculating wattage is a quick process once you know the appliance's amperage and voltage — you simply multiply the two figures. An appliance that uses 110 volts of electricity and 5 amps uses 550 watts.
Applications
From wattage, you can calculate kilowatt-hours, which is the unit by which electricity companies charge. Divide the wattage of the appliance by 1,000 to determine how many kilowatts it uses. Multiply the amount of kilowatts by the number of hours you use the appliance per month to determine how many kilowatt-hours the electricity company charges you for. For instance, a 550-watt appliance uses 0.55 kW of electricity. If you use the appliance for 60 hours per month, you owe for 33 kWh of electricity. Look at your electricity bill or contact the company to find out how much it charges you per kilowatt-hour. As of 2011, the national average is 11.2 cents per kilowatt-hour.