>>5
Actually, we could power the world for a year on the energy hitting the Earth in less than an HOUR.
Since there seems to be some confusion over terminology and units, I'll explain in as simply and as briefly as I can.
A joule (J) is the SI unit of energy. A watt (W) is a rate of energy usage. One watt is a rate of usage of one joule per second (1 W = 1 J/s). Put another way, the total amount of energy used over the course of one second at a rate of one watt is one joule, also called a "watt-second" (1 J = 1 W * 1 s).
Though I won't be using the term here, a "kilowatt-hour" (kWh) is unit of energy, like the "joule"/"watt-second", NOT a rate. 1 KWh is equal to 3.6 MJ (1 kWh = 1000 W * 3600 s).
Global energy consumption is at about 500 EJ per year (which equates to an average usage rate of about 16 TW).
500 EJ = 500,000,000,000,000,000,000 J
500,000,000,000,000,000,000 J / 31557600 s (1 year) ~= 15844043907014 W
~15,800,000,000,000 W = 15.8 TW
Calculating how much energy we can get from the Sun is less straightforward. On average, the Sun delivers about 1366 watts per square meter, which fluctuates about 7% in either direction during the year. "For the whole Earth, with a cross section of 127,400,000 square km, the total energy rate is 1.740 × 10^17 W, plus or minus 3.5%. This 174 PW is the total rate of solar energy received by the planet; about half, 89 PW, reaches the earth's surface." (Quote stolen from Wikipedia.)
174 PW = 174,000,000,000,000,000 W
500,000,000,000,000,000,000 J / 174,000,000,000,000,000 W ~= 2873 seconds ~= 48 minutes
89 PW = 89,000,000,000,000,000 W
500,000,000,000,000,000,000 J / 89,000,000,000,000,000 W ~= 5617 seconds ~= 94 minutes
To capture that whole 89 PW (89,000 TW), though, would mean covering the entire planet in 100% efficient solar panels, which obviously isn't happening for numerous reasons. Which is why so much research is being poured into large-scale orbiting solar farms. Current plans are for at least 10% of the US energy supply to come from space-based solar by 2050 on a budget of about $10 billion. We're talking about satellites with solar panel arrays a kilometer or more long that transmit energy to Earth on microwaves. The satellites wouldn't even need to be in Earth orbit.
http://en.wikipedia.org/wiki/Joule
http://en.wikipedia.org/wiki/Watt
http://en.wikipedia.org/wiki/World_energy_resources_and_consumption
Oh yeah, the OP question.
"Since 50 Mt is 2.1×10^17 joules, the average power produced during the entire fission-fusion process, lasting around 39 nanoseconds, was about 5.4×10^24 watts or 5.4 yottawatts. This is equivalent to approximately 1.4% of the power output of the Sun." (Wikipedia)
The US consumes about 110 EJ a year.
5.4 YW = 5,400,000,000,000,000,000,000,000 W
39 ns = 0.000000039 s
5,400,000,000,000,000,000,000,000 W * 0.000000039 s ~= 211,000,000,000,000,000 J
110 EJ = 110,000,000,000,000,000,000 J
211,000,000,000,000,000 J / 110,000,000,000,000,000,000 J ~= 16.8 hours
Though the above answer is good too, he just started from the 3.3 TW average rate figure from 2005 instead of my 110 EJ total figure, which is a more recent estimate.
http://en.wikipedia.org/wiki/Energy_in_the_United_States