What does the energy efficiency ratings on products mean?

1 Answer
Y.May · Stefan V.
Mar 18, 2016

#"Efficency(%)" = "useful energy"/"total energy" xx 100#

Explanation:

On a product there will be an efficiency number, this tells you how much of the energy produced is useful.

For example, a light bulb may be #20%# efficient. If the bulb has a power of #"100 W"#, only #"20 W"# are useful, light energy, while the other #"80 W"# are waste such as sound or heat.

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