I don’t know anything about energy efficiency, but as an amateur treehugger I question the wisdom of decorative gas lamps.
Outdoor lamps like this one burn 24 hours a day on the corners of many J.C. Nichols subdivisions here in central Johnson County. They don’t provide much light; they’re just for looks. It must cost a bundle, to say nothing of the environmental issues, to keep these eternal flames lit.
Solar-powered street and traffic lights and traffic lights are becoming commonplace. Why not convert to these systems? Barring that, perhaps these lamps could be augmented by light-sensitive on-off switches.