How much electricity does the world use in one day?

Total world power as of 2008 was 474 exajoules of energy annually. Currently man creates 80 to 90% of this power through fossil fuels. The remaining 10% comes from nuclear(10 to 18%), wind(<1%), solar(<.2%), geothermal(<.2%) and hydro (3 to 7%).

This level of power is the would be the total output of 7500 nuclear reactors (based on average build 1999). This power could also be produced by 800,000 hydro electric plants. Putting wind into scale, they would require 1.8 million towers (and associated fossil fuel backup).