Power Inverters are typically used to convert the power of 12 Volt car and leisure batteries for use with domestic appliances that are fitted with a 13 Amp plug such as hair dryers, radios etc. They come in different wattage ratings up to 500 Watts depending on the demands of the application. Step down transformers are used to convert Domestic UK power of 240 Volts to 110 Volts for powering appliances that run on 110 Volts which could either be non-UK appliances like those from the US for example or perhaps UK power tools and site equipment designed to run on 110 Volts for reasons of safety, particularly when power is needed outdoors.