An Olympic-class athlete on a pedal bike can produce 350 watts. If he pedals for 3 hours, he will produce 1 Kilowatt-hour. Out here, a Kilowatt-hour from the electric company costs $0.07. So having a gym of say 40 Olympians all pedalling at top efficiency for a full hour would yeild a revenue stream of (40)(0.35)(0.07)= $0.98 . Less than 1 buck per hour. A solar cell array on the roof would be a much better deal.

I actually thought about this concept as well. The only difference would be hydrogen fuel cells would be involved. You can have these huge gyms where fitness freaks would transfer energy on treadmills and the like which would transfer power to fuel cell banks. These banks would allow transfer energy for other use. The best part is that you would get a discount on your gym membership depending on how much power you transfer to the fuel cell bank.

I think this idea is fantastic. Although considering the economics mentioned above, building a system to do all of this would be expensive and have no real return for gym.

My exercise bike now at least powers itself, you pedal to make it light up.

I like the idea of hooking up a tv to the exercise bike. You can only watch so long as you are pedaling! Prevents couch potato and limits time watching.

Ditto Barry Nalebuff on the exercise machine-powered TV. Maybe people would throw parties so they could take turns exercising and all watch longer on a bigger TV.

The place where this might work is with specialized power needs. As by mach5des, there are exercise bikes that power themselves. My gym has 20 of them. The value is not in the energy, but in the fact that you can put them anywhere. They don't need a power socket.

Along the same line, there might be a market for battery charging by such a device. I would see more promise, however, in a device that the energy produced by sitting down into a battery charging source. That would be easier on a plane.

Props to Barry. There is a device you can purchase now for the average office worker. It creates an break between the power on your monitor, and to work, or use your computer monitor you must keep pedaling. It has variable speed adjustment too so you dont have to pedal like an olympian to get work done, but you still are excersising to generate some electricity for your monitor.

Following up on the comment SVE, Oct 10 2003, the numbers sound small, but scale them up into monthly or yearly savings. He estimated 350 W/bike. Assume one bike investment by a gym. But let's say the utilization/day is 8 hours (this is a busy gym) so 8 hours * 30 days = 240 hours/month of usage. To calculate the monthly savings at ~$0.07/KWhr, do this: Cost/month/bike = (0.07 $/KWhr) * (240hours/month) * (0.350 KW/bike) = $5.88/month/bike. Generating $71/year/bike in electricity could justify the additional capital expense required for such a bike. I'm taking a wild guess that the extra cost over a traditional exercise bike might be $200 so this could have a return in a few years. And of course, we're all not Olympians, so cut the yearly savings in half to normalize us all!

'Green Gym Uses Human-Powered Energy'

http://cleantechnica.com/2008/08/27/green-gym-uses-human-powered-energy/