Here's an example of an office building that has been converted to 100% LED light. The new bulbs consume 48% less energy than those they replaced (mostly fluorescents lights). The workplace in question is the headquarters of Cree, a company in North Carolina that specializes solid-state LED lights. The parking lots, entryways, lobby and conference rooms at Cree’s headquarters are now lit by eco-effective XLamp LEDs. Even the high-pressure sodium parking lights and spotlights were converted to LED lights.Cree wanted to demonstrate that LED lights are a viable option today for businesses and residences. The company claims that their lights render the same type of light that is produced by fluorescents or incandescents. It looks like the LEDs in the photo above are producing a full-spectrum light.
When LEDs replace incandescent bulbs, there is also the added advantage of reducing AC requirements in the summer.
The only method of lighting more energy efficient than LEDs is daylighting (e.g. through the use of sun tubes, for example).
See also: CREE LEDs: As Efficient as Fluorescents