Yesterday, I was reading that new book titled “Energy for a Sustainable World: From the Oil Age to a Sun-Powered Future” by Nicola Armaroli and Vincenzo Balzani.

The book looks pretty interesting, and the figure from “De Rebus Bellicis”( is quite interesting. However what was the funny and witty(or weird) thing was the human-energy algebra done by the writers.

In Chapter 3, “Energy in History”, the writers compare the Roman society and modern society.They first assume human power like a traditional source of power in Watts( , like Watts in CFL or light bulbs. They claim:

  • A (slave) people can work constantly at a rate of 50-80 W (in short bursts 800W momentarily p.29)
  • Working animal ranges from 300W (oxen) to 700-800W (for good horse, p.27)

So what is the cost of modern life in terms of slaves? Answers are:

  • Washing machine: 800W : 10 human slaves
  • Electrical heating: 2.5 kW: 30 human slaves
  • A small European Cutter: 3.5kW (work done with this cutter for one hour equals to a work done by 4 human slaves in whole day-10-12 hours I guess)
  • A medium sized car: 80 kW consumes the energy equivalent to 1000 human slaves
  • A Boeing 747-400 needs 80 MW to take off = 1 000 000 human slaves

And it claims, an average Italian citizen has as many as 55 energy slaves 24/7.

They also carried out a cost of energy by slave and gasoline. Since a slave can produce an amount of 800Wh in one day (in 10 hours constantly) and one liter of gasoline’s energy content is 12.9 kWh. So 1 liter of gasoline’s energy = 16 human slaves in all day. That means €0.03 for one human slave/day.

See how cheap the services granted by fossil fuels and modern technology.


Energy for a Sustainable World, Nicola Armaroli and Vincenzo Balzani, Wiley -VCH. , 2011

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1 Response to "If a human slave is 80 Watt/hour, energy algebra of modern life is…"

  1. Solar panels Said,

    sun power energy is popular in are which truly value energy.

    Posted on March 12, 2012 at 8:24 AM


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