>>976131> less efficient than derailleurThat depends on many things: State of derailleur and chain, dirt and gear.
The first charts show that a derailleur is more efficient @200 watts than all hubs. @50 watts it is less efficient than most.
The second chart shows that derailleur efficiency also varies with gears chosen (crosschaining).
Both tests were done with new components. With worn and dirty components, the derailleur will be less efficient.
Sources:
http://fahrradzukunft.de/16/wirkungsgradmessungen-an-nabenschaltungen/http://cozybeehive.blogspot.de/2012/01/factors-affecting-bicycle-transmission.html 