Originally Posted by
Road Fan
I don't see why the German law means you must put out 3 watts no less and no more, unless the German authorities were trying to eliminate extra-bright lights on the public roads. It that case the spec needs to ahve an upper and lower bound, and I don't recall that it does. I read it more than 10 years ago!
Today I'd suggest just buy a Luxos B or U.
The German law does not require a dynamo to put out exactly 3W and no more or less...
It is designed to make sure that AT LEAST 3W are available at a speed of about 15kph (assumed to be a typical cycling speed for commuter type cyclists) and that a certain quantity and quality of light is produced.
What limits the power generated from dynamos are size/weight/cost, and to some extent physics.
I'd go for the Luxos B as the best value--which I did, though I also use an IQ Fly RT senso