> That amount of energy can't be found in renewable sources only.

1.) overall humanity is still very inefficient at extracting productivity & comfort from energy. e.g. there is no inherent reason why buildings should need any energy flow to stay at a comfortable temperature. GP did not argue against reducing energy needs but against trying to make people reduce their quality of life.

2.) even at the current consumption I'm not so sure that 10Bn people could not be sustained. there's a hell of a lot of energy incident by the sun, it's just a matter of storing it where we have scaling issues. a whole bunch of battery tech ideas could help with that.

Overall I don't think we're that far from mass producing net energy positive houses (solar roof + industrial battery + near perfect isolation through e.g. low pressure zone in a double wall system). Inhabitants could either sell their energy on the market or use it for their transport needs.

The arrogance of software engineers to believe that a few joules saved would make a difference. Humanity can spread to the stars and we still won't make a significant dent in the overall entropy changes in the universe even after billions of years. Energy consumption is a false herring for moral superiority and control. Replace the traditional Church with environmental activists and you have your modern climate change politics. Climate change is primarily due to increased heat capture caused by emissions. We have plenty of ways to generate clean energy without harmful emissions, nor excuses for social control.

Energy consumption as it relates to the generation of latent heat at the planet surface is not a red herring though.