Originally Posted by
jputnam
There's quite a range. A standard 9004 automotive halogen headlight puts out 700 lumens per headlight, so 1,400 for the pair.
BUT, note that auto light makers are often held to their claims, while bike light makers routinely engage in wild puffery. Many nominal 1,000-lumen bike lights actually put out something around 5-600.
Yeah 9004 (which I consider to be the worst crap halogen headlight bulb there is) is 700 lumen for low beam, 45-watts, 12 volt. 9006's are 1,000 lumens with a 55-watt 12V draw. A standard Philips D2S xenon HID capsule is rated at 3,200 lumens for the 4300K color temperature version (used as OEM equipment in cars), with a nominal 35-watt 12V draw from the ballast (much higher voltage used initially to fire up the bulb).
But those are meant for cars doing 70 MPH down the interstate at night. A bicycle light doesn't really need to be anywhere near 3,000 lumens in order to put down more than enough light.