The other day, I started thinking about the different energy sources humans have exploited and their evolution: trees (charcoal), fixed water (water wheels), animal (as labor), animal (fuel, as in whale oil), hydroelectric, coal, oil, natural gas, nuclear fission and wind-electric. After I made the list, I thought, "what's left?"
Here's the answer according to a USGS report:
oil: 18.42 ZJ (zettajoule, or 10^21 joules)
natural gas: 15.7 ZJ
coal: 290 ZJ
Uranium: 2 ZJ (up to 1000 ZJ in fast breeder reactors)
Those are global estimates.
Here's the breakdown of where we are getting our energy:
natural gas: 23%