originally posted by D*Alex
Mine is 6v, 3w, for a grand total of 18 amperes.
Sorry D*Alex, but 6V and 3W is 0.5 amperes.
I have two, yes
two, NiteRider NightOwls, 10W each. The battery will last for over 2 hours on each. I run one at a time unless it is really dark or raining. I live in Atlanta (lots of traffic) so the more the merrier.

I want to see and be seen.
Ten watts should be plenty for riding at night. Just be sure the Night Hawk model you get (you didn't say which one) will last for 2 hours.
And don't forget a taillight.