Originally Posted by njkayaker

Wind resistance gets worse faster as you increase your speed.

http://www.exploratorium.edu/cycling/aerodynamics1.html

For a 200 lb cyclist at constant speed:
5 mph -> 1.46 watts
10 mph -> 11.75 watts
15 mph -> 39.66 watts
20 mph -> 94.01 watts
25 mph ->183.62 watts