I just bought Gerbing's heated insoles, gloves,
pant liners, and jacket liner. I know the entire
outfit recommended a 250+ watt alternator. I
can't remember the exact numbers, but I did
research it and found that the 9 has plenty of
juice to run the entire outfit.
Also, I took the bike out a couple weeks ago when
the tempatures dipped into the low 50's. I wore the
entire outfit, sans the insoles (they hadn't arrived
yet), and had it on full blast (yes I was baking!),
and noticed no adverse reaction from the bike. It
ran just as strong as ever, and never seemed to
be losing power (electrical power).