Originally Posted by
elbows
I'd completely forgotten about the i-Light. But it seems to have pretty high drag with the light turned off (almost as much as when it's turned on, in the numbers I found). Not a big deal for commuting, but on long rides those extra few watts probably add up.
It has indeed as much drag when off, but if you're like me and you always have it on because of the tunnels and such, it shouldn't really bother.