Here's an interesting calculation from physicist Tom Murphy. Let's say our current global rate of energy use is 12 terawatts, which gives each citizen 2000 W of energy. (There's actually a 2000 Watt society in Switzerland.) If our economy grows by 2.3% per year, in 100 years, it will require 10 times this amount of energy (120 TW). In 200 years, it will need 100 times the current level (1200 TW). And so on. Now imagine we could surround the sun with 100%-efficient solar panels and capture all the energy spewing out of it. Our 2.3% per year economy would consume all that energy 1350 years from now. In 2500 years, our 2.3% economy would require all the energy from all the 100 billion stars in our galaxy. --- Source: https://dothemath.ucsd.edu/2011/07/galactic-scale-energy/