Simply enter the unit cost of your electricity and plug an appliance or extension lead into the power monitor and the LCD screen will show you the running cost of the plugged in appliances over a period of time,ideal for seeing how much that full kettle actually costs you to boil or how much that tumbledryer uses per cycle,these power monitors also allow you to see other useful data such as time active, kilowatt hours used (as found on your electricity bill), active watts consumed, voltage from the socket, amps used and frequency of the electricity (mains power is normally 50Hz),a very handy gadget if you want to find out how much the devices in the home actually cost to run with a view to reducing your monthly electricity bil,price includes vat and delivery.