Originally Posted by
mikhalit
Look
here for equations. The relationship for rotational kinetic energy for different wheels will be linear. A wheel with Alfine 8 will be about 45-50% heavier than one with Deore hub and cassette. Even if you don't consider the small radius of the IGH hub the difference in the required energy will be less than one percent of total energy needed to get a 200 pounds rider+bicycle combination going.
The relationship to get a larger wheel up to speed is greater which I agree. But what happens if you have two wheels the same size with one hub weighing much more than the other? How much energy would I expend after 10 miles, 20 miles 100 miles? I'm sure after 100 miles, the amount of energy used would be significant.
Also, the weight of a Deore cassette is .78 lbs when added with the hub brings it to 1.88 lbs. Therefore, this difference is not 40-50% at all. The Nexus 8 weights nearly 100% more than a Deore hub and cassette combined! (3.7 / 1.88)