Made by one of the leading manufacturers in the industry, the Topow ST Series step up / step down voltage transformers offer you a safe, reliable, affordable and convenient solution to converting voltages from 110-120 volts up to 220-240 volts, or from 220-240 volts down to 110-120 volts for both home use and industrial applications. The ST-20000 is rated at 20000 watts maximum. The manufacturer recommends you purchase a transformer that is 25% higher than the wattage you need. You should know that you will never damage your appliance with a higher voltage transformer, however if you buy one that is not powerful enough, it will not work. Remember to leave at least a 100% slack for the transformer. Some items, such as laser printers and power tools, spike when you turn them on. For these types of situations you need to buy a transformer that is at least 3 times the item's capacity. Use Amps to calculate Watts: Volts (times) Amps = Watts : For example 110 Volts x 5 Amps = 550 Watts. Ships in a solid wooden box with Styrofoam inserts for maximum protection. This transformer comes with terminal connectors - hardwire input required.