Thanks it is good to know that the sidewall generator system eats up more than 5 watts. If there are any trainers with power meters, then maybe a person could ride at 100 watts for a while and then go to 105 watts and see the precieved difference in the effort required. Going back and forth between the power levels over a period of an hour or two should be helpful. I am not sure but I think that I would notice the difference. But if a person jumped on the trainer and rode for an hour without looking at the power meter they probably could not tell if it was set to 100 watts or 105 watts. But then again I really don't know because I don't have any way to test my guesses.