Doing the best or right thing depends on right thinking. So on paying attention to how much, and not just describing with words. Fortunately you can use pictures of how much to help your thinking.
How much power is measured in watts or kilowatts (thousands of watts). This number is often written on the outside of an appliance, where you might find watts abbreviated to W and kilowatts abbreviated to kW.
How long an appliance is on for might be measure in hours, minutes or seconds. You decide this with a switch. An automatic switch might do it for you at home:
Some devices, such as overnight heaters might be controlled by two switches for time and for temperature.
How much you'll get charged is set by the power and how long. A high power device might cost as much in a day as a low power device that's left on for longer.
The height of the box shows the power. The width of the box shows how long. The are shows what you'll have to pay for – the kilowatt-hours. kilowatt-hours = kilowatts × hours