This reminds me of an old (misleading) graphic in Wired magazine suggesting that people on treadmills could be significantly reducing their electricity bills.
Things like laptops and some desktops could be easily powered by bicycle, though. I managed 220W for 30 mins, and could probably idle 50-75W for hours, which is more than enough for multiple laptops.
Some city noticed changes in consumption when new houses had meter installed on ground floor rather than in the basement.
They're advertised as saving energy which I think is a bit misleading as it's only based on this phenomena
It was probably the worst energy scheme they could have spent the estimated £16bn on. That much in insulation would have slashed domestic heating costs, but as ever that's a much less sexy project.
Note that these are very generous estimates, but it does demonstrate how silly the idea of trying to generate electricity by capturing exercise output is (in a purely economic sense).
It's a lot more than that. Even a fit (healthy, but not necessarily peak athletic shape) adult man will have about 15% body fat, 20% for a woman.
I heard pro cyclists can reach up to 2kW. I managed to make 500W on a rowing machine for 5 minutes, but I'm a couch potato. I believe 400W is a normal rate for cyclists. When you are sitting, your body already produces about 100W of heat.
This hugely depends on body weight / gender / training levels etc., body weight being a big deal since that’s what you’re transporting. So the other way folks measure output is W/kg of body weight.
A beginner adult male will be in the 100-200W zone, around 0.5-1.5 W/Kg. Usually anyone can train themselves into the 200-300 (3-4 W/Kg) zone which is the recreational pace - the groups of cyclists you see on the road. Beyond 300 ftp (150lb body weight) (4-5 W/kg) you’re reaching race pace. The ones you see on screen have upwards of 5-6 W/Kg FTP output. They obviously have other constraints around putting this output at the end of a 200km ride for 20 mins etc as well, which makes it extra hard.
Finally we come to the KW numbers - all these folks have two kinds of muscles (fast twitch and slow twitch). The sprinters are saddled with a higher proportion of the kind of fibers that can allow huge spurts of power - they put out about 1000-1500W for about 5-10s. These are probably what you’re thinking of. This is pretty much an end of ride (or a sprint section) empty your tanks effort.
Semi related tidbit: track cyclists are a middle kind of beasts here: they put 600-1000W for a couple of minutes but don’t have to worry about riding 200kms to get there.
On the other hand, it is possible to imagine lifestyles enhanced by various 10W contributions. 10W for heated clothing. 10W for a laptop. 10W average to power a several km electric bicycle or Aptera-size commute. And so on.
Based on Ali Express, heated clothing (5V power in a pocket) is popular enough in China.
Not saying it's a good defense though.
Even if you don't generate much, at least your biomechanical efforts are used somewhere.
And wasn't it Mumford who observed that given the time it takes to earn the money to buy a car, on average it can be faster to walk than to drive.