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How does a gallon of diesel become light?

A small diesel power plant, one step at a time. Press the steps in order and watch the machine do each one. The numbers come from a real 500 kW generator, with sources at the bottom.

Press 1 to start. Each button plays one step on the machine.
DIESELRPMkWVOLTSSTOP

Inside one cylinder

stopped

One gallon of diesel

Day tank0 gal
Fuel use0 gal/h
Engine0 rpm
Alternator0 V
Power out0 kW
Average US homes it covers0
Gallon burned0 gal
Electricity from it0 kWh

The big idea: a gallon of diesel holds about 40 kWh of heat, and this generator turns 14.1 kWh of it into electricity. The rest leaves as heat.

How the numbers were worked outOpen it to see every sum and all 8 sources.Click here again to fold it away.

How much heat is in a gallon depends on whose count you use. Caterpillar's spec sheet counts 37.7 kWh (its "lower heating value"), so 37% becomes electricity. EIA counts 40.3 kWh, so 35%. The panel uses EIA's count.

Where "about 390 homes" comes from: 500 kW, less the 5% lost in the wires on the way, leaves 475 kW. An average US home used 10,791 kWh in 2022, which is 1.23 kW over the 8,760 hours of a year. 475 ÷ 1.23 is about 386 homes.

Where the numbers come from

  1. Fuel use at 25, 50, 75 and 100% load (in litres an hour, turned into gallons here), 500 kW, 1,800 rpm, 60 Hz and 480 V, and its fuel basis (42,780 kJ/kg, 838.9 g a litre): Caterpillar C18 500 ekW technical spec sheet DM9831-02 (2017)
  2. Heat in diesel (137,381 Btu a gallon) and in a kWh (3,412 Btu): EIA, British thermal units (Btu)
  3. One US gallon is exactly 3.785411784 litres, used to turn the spec sheet's litres into gallons: NIST Handbook 44 (2026), Appendix C, tables of units
  4. About 5% of electricity is lost in transmission and distribution (2018 to 2022): EIA FAQ, how much electricity is lost
  5. A US home used 10,791 kWh of electricity on average in 2022: EIA FAQ, how much electricity does an American home use
  6. Diesel lights in hot squeezed air, with no spark: Britannica, diesel engine
  7. A magnet moving inside a coil of wire makes electricity flow in the wire: EIA, how electricity is generated
  8. Transformers step the voltage up for the long wires, and down again before homes: EIA, delivery to consumers

Between the spec sheet's four loads, fuel use is drawn as a straight line. The ship and the shore tank, the day tank, the crank speed and the three houses are this model's own choices, and steps 1 to 3 are not timed to real life. The machine is a drawing of no particular brand. The speed badge shows how much faster or slower than real life a step plays.