Energy Efficiency is the measure of how much useful energy an electrical device produces compared with the amount of energy supplied to the device.

• Energy out – measure of how much useful energy the device puts out to do its task
• Energy in – measure of how much energy the device requires

A light bulb uses 100J of electrical energy and produces 35 J of light energy. Calculate the percent efficiency of the light bulb.

A toaster oven uses 1200J of energy to produce 850J of thermal energy. Calculate the percent efficiency of the toaster oven.