Would it be worth it for a gym to have certain exercise equipment?
Presumably you mean an exercise bike or a rowing machine. I was a pretty good cyclist, I could churn out 200watts all day long and considerably more than that on a 20 second sprint. Obviously, I was well short of a pros output. Joe Blow in the gym might manage 150 or 200 watts an hour. Although most amble along at what I guess is 100w an hour. Few people stay on a bike for an hour. Let's assume there's 3 bikes spinning continually and making 450 watts combined. That wouldnt run half a treadmill ( 1500+w motors). It would run a couple of double tube lights. Or 3 small fans. In Thailand I pay about 5 BT a unit ( 12 cents) for my electric. Factor in the cost of a genny fitted to the bikes, people getting on and off, causing voltage drops and motor damage, and it would take me a 100 yrs to recoup my expenditurein my imaginary bike powered gym.