[MrForbes]

The motive force required to move a 100 lb robot is usually not 100 lbs, it's some percentage of that. But it depends on rolling resistance, how much acceleration you want, whether you're going up hill or down hill, if you're turning, etc. And if it's a balancing robot, you're going to have a balancing load...you will probably be driving the motors in an oscillating manner to keep the robot upright, so you will be using power just to stand still.

This is very hard to figure out with numbers....which is why I suggested you do it empirically. Try it and see what happens.