It is important to check the spec. In a back issue of ReNew magazine it was pointed out that a normal incandescent globe gives 10 – 15 lumens per watt (light output per unit of energy used). A halogen lamp rated at 20 l.p.w. and fluorescent lamps at 60+ l.p.w. At the time the article was written LEDs rated at between 15 and 30 l.p.w. but were improving rapidly. The article also points out the need to consider the efficiency inverters and transformers that may be built into some lights. For example 12 volt fluoros have a built-in inverter that may be quite inefficient. Often hard to discover these detailed specs.
It is worth looking at this article and comments on the [url=http://www.choice.com.au/Reviews-and-Tests/Household/Energy-and-water/Saving-energy/Compact-fluorescent-lightbulbs/Page/Compare%20CFLs.aspx]Choice web-site[/url]