I agree 600kcal is on the high side, but I don't think it's as far off as you think. Most estimates I've seen are between 300-500kcal per hour, depending on eff

I agree 600kcal is on the high side, but I don't think it's as far off as you think. Most estimates I've seen are between 300-500kcal per hour, depending on effort. It depends a lot on the bike and on the route. On a road bike going down a straight, flat road wearing lycra 20km/h is zero effort. On a city bike loaded with groceries going through urban environment with a bunch of traffic lights 20km/h average is quite an effort.