The Facts About Energy Efficient Light Bulbs

[RobertSmalls]

Wikipedia says the opposite about low-pressure sodium lamps:

LPS lamps are the most efficient electrically-powered light source when measured for photopic lighting conditions—up to 200 lm/W, primarily because the output is light at a wavelength near the peak sensitivity of the human eye. As a result they are widely used for outdoor lighting such as street lights and security lighting where faithful color rendition is considered unimportant.

High pressure sodium has additional phosphors and Sodium electron excitations and is a whole different ball game.