The question is: how much time do you spend accelerating?

For me, it only seems to take a few pedal strokes to get back up to 15-20mph. By the time I cross an intersection I can be back up to speed. Probably only 5-10 seconds? So on a 90-minute ride with 30 stops, I'd spend 2.5-5 minutes accelerating and 85-87.5 minutes cruising. Assume cruising is 200w and accelerating is 500w. Average power would be 208-217 watts. Less than a 10% difference. In my case, I probably only stop 5-10 times during my normal 30-mile training route, so the impact is even smaller...