Originally Posted by
achoo
Assuming 0% grade and no wind, it takes 52% more power to go from 20 mph to 23 mph. On level ground, with no wind, power to overcome aerodynamic drag is proportional to speed cubed. At those speeds, aerodynamic drag is by far the largest force to overcome.
...snip...
Yes, see this
bike speed calculator for a rough estimate of power needed. It's not like lifting, where 45% more power takes you from 350 lbs to 507 lbs. On a bike, it's "just" a few mph faster. Riding in a more aero position can help, and drafting a group of riders can require perhaps 30% less power.
Taking the calculator's default settings:
On the drops:
20 mph is 176 watts
23 mph is 257 watts. 46% more power to go 15% faster.
An aero tri bike:
20 mph is 151 watts
23 mph is 219 watts. 45% more power.