… the 20th century saw a nearly 40-fold gain in useful energy [i.e. energy available for human use]; since 1800 the gain was about 3,500-fold.
To get an even clearer picture of the magnitude of these changes, we should express these rates in per capita terms. The global population rose from 1 billion in 1800 to 1.6 billion in 1900 and 6.1 billion in the year 2000, and hence the supply of useful energy rose (all values in gigajoules per capita) from 0.05 in 1800 to 2.7 in 1900 and to about 28 in the year 2000. China’s post-2000 rise on the world stage was the main reason for a further increase in the global rate to about 34 GJ/capita by 2020.
An average inhabitant of the Earth nowadays has at their disposal nearly 700 times more useful energy than their ancestors had at the beginning of the 19th century.
Moreover, within a lifetime of people born just after the Second World War the rate had more than tripled, from about 10 to 34 GJ/capita between 1950 and 2020.
Translating the last rate into more readily imaginable equivalents, it is as if an average Earthling has every year at their personal disposal about 800 kilograms (0.8 tons, or nearly six barrels) of crude oil, or about 1.5 tons of good bituminous coal. And when put in terms of physical labor, it is as if 60 adults would be working non-stop, day and night, for each average person; and for the inhabitants of affluent countries this equivalent of steadily laboring adults would be, depending on the specific country, mostly between 200 and 240.
On average, humans now have unprecedented amounts of energy at their disposal. The consequences of this in terms of human exertion, hours of physical labor, time for leisure, and the overall standard of living are obvious. An abundance of useful energy underlies and explains all the gains—from better eating to mass-scale travel; from mechanization of production and transport to instant personal electronic communication—that have become norms rather than exceptions in all affluent countries.
Tracing the trajectory of useful energy deployment is so revealing because energy is not just another component in the complex structures of the biosphere, human societies, and their economies, nor just another variable in intricate equations determining the evolution of these interacting systems. Energy conversions are the very basis of life and evolution.
Modern history can be seen as an unusually rapid sequence of transitions to new energy sources, and the modern world is the cumulative result of their conversions.Vaclav Smil – How the World Really Works: The Science Behind How We Got Here and Where We’re Going [amazon link]