grolby

No. Not even a little bit close. It's tempting to just add the numbers together, but it's not that simple. Think about it - how much power does it take to stand still in a 25 mph wind? The answer is zero watts, not the power it takes to ride 25 mph. A wind, even a strong one, is not the same as pushing aside still air. Head over to Bicycle Speed (Velocity) And Power Calculator and play with some numbers if you want to see for yourself how it works theoretically. If I plug in my numbers (65.5 inches, 125 lbs, on the drops) and leave everything at the default values, I calculate 495 watts for me to pedal 30 mph in still air. Hold power constant and give me a 25 mph headwind and speed drops to 16.6 mph. That's a substantial decrease in speed, but it's not 5 mph! In order to ride at 5 mph in that 25 mph headwind, I calculate 80 watts. According to kreuzotter.de, then, riding at 5 mph with a 25 mph headwind is equivalent to riding at just over 15 mph, NOT 30 mph. This works the other way, too - turn that 25 mph headwind into a tailwind and you don't get to go 30 mph for the power you would normally need to go 5 (which is the logical conclusion of the same specious reasoning that says 5 mph + 25 mph wind = riding at 30 mph.

There's no doubt that a 25 mph headwind is much stiffer than most people realize, but riding 30 mph is also much harder than most people realize. I have not attempted to measure my actual power output at 30 mph by myself, but even if it is less than 495, I can't maintain anything close to that for longer than about 40-60 seconds. 80 watts or anything in that ballpark, by comparison, is extremely easy even for a small rider like me. 80 watts is such low power that I find it frustrating to go that slow.