My battery range on my puny 250W conversion can be between 16 miles and 9 miles. A lot of hills (with short stretches of 15%) decrease range to 12 or 13, but my shortest ranges are always on windy days 9 or 10 miles. My bike is more susceptible than most due to 5.4 ah battery, low power, and more upright seating position.Headwinds are worse than hills. With a hill you can see the beginning and the end. Winds are invisible and never end until you turn around. Big nasty battery drainers.
On a windy day, I'm start staring at my GPS after 4 miles or so, calculating route, wind direction and speed, and the range anxiety kicks in pretty bad! No wind, I don't worry that much if turnaround is at 6 miles, even with 1,200+ feet of vertical.
The other thing about wind: You can't tell how strong it is because you're moving, making any meaningful range estimation not just difficult but impossible.