Confirm that your device uses 120V by checking the information attached to the back or bottom of the device, on the electrical cord or the device's instruction manual. Note that in most situations 110V and 120V are interchangeable; thus, the following steps are applicable to 110V devices as well.
Check the device's information for its wattage. If amps are presented instead of watts, multiply the voltage and the amps to get the wattage value. For example, if a 110-volt device uses 0.5 amps, the calculation would be 110V (volts) x 0.5A (amps)= 55W (watts). Thus, the wattage for the item is 55 watts.
Look at the information located on the body of your step-up transformer to determine its wattage capacity. You can use your 120V device with the transformer as long as the device's wattage doesn't surpass 75 to 80 percent of the transformer's wattage capacity.
Plug the step-up transformer into the 220V source, then plug the 120V device into the transformer. Turn on the transformer's power (often in the form of a switch) and your product is free to use without worry of damage due to voltage differences.
