Turning On the Lights: Conversions and Efficiencies

June 1, 2023

Flipping a light switch begins a sequence of energy conversions before you ever see the light. Tap the switch to begin the journey of energy from the fuel to your light bulb. Tap on the left or right of the image to continue.

Every time energy is converted, some of it is lost. The efficiency (η) of the entire process is the product of the efficiency of each conversion. In this example, only 0.6% to 1.1% of the energy contained in the fuel becomes useful light, while the rest is lost as heat.

Large power plant boiler (makes steam)E1 = 90 – 98%c→t
Large steam turbine (makes motion)E2 = 40 – 45%t→m
Large electricity generator (makes electricity)E3 = 98 – 99%m→e
Utility electric grid (distributes electricity)E4 = 94 – 95%e→e
Traditional incandescent lightbulb (makes light)E5 = 1.8 – 2.6%e→r
Total: ETotal = E1 × E2 × E3 × E4 × E5ETotal = 0.6 – 1.1%c→r
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