Pros and cons of Bicycle Power
Hub dynamos are generally considered the best but require a wheel to be rebuilt if retrofitted (the existing rim can usually be reused). Some bikes are available with hub dynamo lighting systems as a factory option; this can be very cost-effective.
Some riders consider the output of dynamo lighting insufficient. Others report that it is adequate to see on dark roads at speeds up to about 20 mph (32.19 km/h), (single 3 W) or more if a 12 V system is used. LED headlights typically give 2-3 times the light output of a halogen lamp for the same power, due to their greater efficiency.