In 2008, Earth's commercial power systems provided ~225 watts of thermal power per person (225 Wt/person) to its 6.67 billon people. This totals to ~15 terawatts of thermal power (15 TWt = 15x1012 Wt = 225 Wt/person x 6.67•1010 people). However, they need the equivalent of 6,000 to 7,500 Wt/person of sustainable power for sustainable prosperity. So, by 2050 ten billion people will need ~75 terawatts of thermal power.