I just did a 27 mile ride Sunday...straight N-S with winds @ 10-15 with an occasional gust from the N. So...1/2 of the ride, I had a nice tailwind, the other half, right into it. There was only 453' of elevation change over that distance so it was fairly flat. Out was 21-24mph ave and back was 16-18mph average. My overall average came in at 18.3mph (factoring in traffic, stops, etc). The first half was rather easy and the second was not easy...I had to work my rear off to get that 16-18mph.

All in all, having taken that exact same route in light to no wind...I average 18-19mph with sustained medium effort. So...Sunday, I was right there but the first half was pretty easy, the second half sucked. In the end, I was no faster/slower and probably didn't burn any more calories overall figuring how easy the first part was.

In the end, I'd rather have light winds than heavy. The tailwind doesn't make the headwind worth it. Then again...nature is nature and we deal with it.