When I was at Peloton a long time ago, someone proposed an April Fools’ joke where we could announce a dynamo add-on that would let you power your house from your bike.
The math isn’t as bad as you might think: 200Wh (about a 60 min, somewhat intense ride) seems to be about 20 minutes for a H/B100. Still 3x, but not bad at all!
I remember the idea being dismissed quickly because people would likely actually want it.
200W is pretty good FTP for an "untrained" cyclist. FTP is the maximum you can sustain for a single hour, but you're not going to do multiple back-to-back.
Obviously the peloton crowd is biased towards people who will have better endurance and higher FTP, but basically the upshot is you could run one card for one hour with the effort of a 100km long ride which most recreational cyclists do once a week.