This document discusses lighting efficiency and power density. It begins by asking about the differences between various lamp types from an energy efficiency perspective. It then discusses luminous flux, illuminance levels, and how to estimate the lighting power density for a house by counting lamps, determining lumens and recommended illuminance levels for rooms, and calculating watts per square meter. Finally, it outlines steps for determining the lighting power density for spaces by establishing illuminance levels, calculating lumens and watts, and verifying if the power density meets regulatory limits.