I think you dropped a zero. I get an average output of about 200 Megawatts which is the size of a moderately small generator. A typical coal fired generator puts out about a 1000 Megawatts. Replacing the energy of ONE moderately small generator with the energy of a BILLION people working their butts off for 20 hours a week is far, far beyond insanity.
I bought a key exactly like the one in the panel here:
http://images.channeladvisor.com/Sell/SSProfiles/23000010/Images/1/4400%20PHOTOSHOPPED.jpg
If a human being is capable of providing 0.1 HP of power and it is convertible to energy at 100% (which is impossible), then we are talking about 74.6 W of output power.
Pedaling for 20 hours will produce 1.492 KWh not KW.
Obviously 1 billion people therefore will produce 1,492 GWh (Giga Watt Hours) - which is nothing to sneeze at.
It takes a nuclear power plant to produce 1,000 MW. In fact the largest nuke plant in US is Palo Verde 2 with an output of 1,335 MW. The largest power plant in the world is ITAIPU which is a hydro plant with an output of 12,600 MW.
Thought I sort this out.