Meet the characters
How much is vital
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.
- show how much power (the watts or kilowatts to run a bulb or toaster) with an arrow
- show how long the appliance is on for (the hours in a day) with a pie. -connect the power and time to the energy you'll pay for using a cost box
- show how much energy you have to pay for with a bar (the kilowatt-hours)
How much - power
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 - hours, minutes or seconds
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:
- for temperature controlled things, like an oven, a room heater, a water heater,
- after a number of hours, minutes or seconds, perhaps set by you on an oven or microwave.
- at certain times of day: perhaps there are heaters that come on overnight.
Some devices, such as overnight heaters might be controlled by two switches for time and for temperature.
How much you 'use'- the cost box
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
