The total US prisoner population in 2008 was 2,424,279 people, and an individual can produce 150 watts when peddling moderately on a stationary bike which would make for a total of 363,641.85 kilowatts per hour (kWh) produced if everyone peddled. With the average price of electricity being 12¢/kWh in the US, if every prisoner exercised for 2.5 hours a day, that would amount to $109,092 in energy cost savings each day, or nearly $40 million a year!
Sheriff Joe Arpaio was concerned about the waistlines of some of the inmates at his Arizona jail, so he had an idea. The sheriff brought in an electricity-generating stationary bike and hooked it up to a television set which is powered by the peddler–and if the prisoners want to watch TV, they have to exercise. Arpaio calls his system “Pedal Vision,” and he thinks it may be just the thing to get his inmates in shape.
– from treehugger.com