That question is not complete. The true question is "How many people can the Earth support at a particular energy-usage level?" A good example would be "How ma

That question is not complete. The true question is "How many people can the Earth support at a particular energy-usage level?" A good example would be "How many people could the Earth support at the European energy-usage level?" That answer to that would be larger than having the population at the US energy-usage level, and smaller than having the population at the African Nomad energy-usage level.