35 years of global energy efficiency gains reflected in the world's GDP

[GliderGuider]

2. If the economy was truly decoupled from energy

...we could get positive economic output with zero energy expenditure (like a perpetual motion machine).

Right now two thirds of the growth of GDP comes from increasing energy consumption, and one third from increased efficiency. But the ability to increase efficiency depends on the energy expenditure being there in the first place.

Economies run on energy. While we can increase the efficiency of any economic activity that requires the transformation or movement of materials (up to some point analogous to the Carnot limit of classical thermodynamics), we can never uncouple the economy from its motive power. If we were to stop increasing the energy supply right now, and maintain constant consumption, the most economic growth we could expect is 1% per year - a rate that would gradually decline over time as we approached the economy's efficiency limit. When that limit was reached, growth would stop.

This is why, despite a 40% improvement in efficiency, our energy consumption has never declined during times of economic growth.