Example 1
800 J useful from 1,000 J supplied corresponds to an efficiency of 80%.
Mendeleev
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Physics tools › Energy efficiency
Mendeleev · Physics
Energy efficiency
Efficiency compares useful energy obtained with the energy supplied to a system.
Formula usedη = Eᵤ/Eᵢₙ
Calculate
Energy efficiency
What do the symbols mean?
ηefficiency
Eᵤuseful energy
Eᵢₙinput energy
Two worked examples
Example 2
At 75% efficiency, a device receiving 2.0 kWh delivers 1.5 kWh as useful energy.
Good to knowFor an ordinary energy converter, efficiency cannot exceed 100%.