Originally Posted by
rumrunn6
Spot checks suggest that can be 50-100% high.
25-35 kcal/mile is a more reasonable assumption without better data.
1 Watt = 1 joule/second, so 100W in 1 hour = 360,000 joules or 360kj.
1 Calorie = 4.2kj although cycling metabolic efficiency is never better than 25% so you can approximate 4 Calories in = 4.2kj out and round to 1 Calorie in = 1 kj out.
On "flat" terrain out-and-back using a power meter with +/-1.5% accuracy I measure about 100W averaging 15 MPH for 360 Calories / hour and 24 / mile; 150W at 18 MPH for 540 Calories / hour and 32 / mile; and 200W at 20 MPH for 720 Calories / hour and 36 / mile.