Originally Posted by plin
Example : 500 kj would be 119 kcal. however, the body is about 20 - 25% efficient, which means that you expend 4 - 5 times the energy, i.e., ~ 500 kcal. So basically in the end to get the number of calories spent in one hour, just take your average wattage for an hour and multiply by 3600(seconds in one hour) then divide by 1000 (to get the number in kilo calories).
An interesting sidebar...
Read, just a few days ago that Eddy Merckx, back in his prime underwent a test for 'power'. Turns out he was able to maintain over 450 watts for an entire hour (455 was his average) without reaching 'failure' (not sure that is the right term). Not done up to that point.
Using your formula that's a prodigious 1638 calories for the hour...
one would asume that subsequent hour record holders would be up around there as well.
Anyone have similar comparo numbers for riders from later eras (Hinault, LEmond, Indurain, Armstrong, Ullrich, etc...)?