Analysis of world data indicates that 4000 kwh per year per capita energy is needed for the current top level of human development. About 1000-2000 kwh per year per capita is needed to get out of the worst quality of life and shortened life span. Per capita electricity usage also correlates to per capita income. Both correlate to life expectancy and quality of life.
Those nations with per capita electricity of 2,000 kWh/year (1/6 US use and an average power of 230 W) do achieve GDP of $7,500 per capita, which leads to sustainable birthrates.
Average power of 460 Watts (7 days a week 24 hours a day) would be needed for 4000 kwh/year.
If world population was 10 billion then this would be 40 trillion kwh/year.
Read more about this here: Nextbigfuture.com