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It is important to know how efficient a device is. With this knowledge, you can compare products and get the right product for your needs. In this activity, you will learn how to calculate how efficient a device is at converting input energy into useful output energy.

The efficiency of a device is the ratio of the useful output energy to the input energy. The more input energy that a device converts to useful output energy, the more efficient it is.

Let's say there are two electric kettles for sale. Kettle A is $19.99 and is 45% efficient. Kettle B is $23.89 and is 64% efficient. Which is the better buy?

Even though Kettle A costs less, Kettle B is the better buy. This is because it is more efficient. So over time, it will use less electricity to do its job, saving you money in the long run.

You can calculate how efficient a product is by using a formula. The following video helps explain this.

Click on the Play button to watch a video that shows more examples of how to calculate efficiency.