Do LED lights really save energy?
Compared to incandescent bulbs, pretty much every technology beyond a flaming wooden stick provides more light for less energy. At the other end of the efficiency spectrum, putting in a skylight or solar tube has zero energy costs during daylight hours (unless you do it badly, necessitating additional air conditioning or heating).
LED lights are available for purchase have finally overtaken fluorescents in practical efficacy. For example, TCP makes a “standard” (A19 or E26) base bulb that draws 15 watts for 1650 lumens, giving 110 lumens/watt. Tube fluorescents are still well below 100 lumens/watt, more typically around 90, and compact fluorescent bulbs well below that.
And LED lights are reasonably priced now, under $3 for an 800 lm, 8 watts (“60-watt equivalent”) bulb from U.S. retailers.
Standard (T5 or T8, say) Fluorescents with electronic ballasts are still probably a little more efficient than LED “bulbs” at converting 120 VAC into useful light, but it’s gotten very close in the last few years as LED flood lightsefficiencies have improved greatly. Standard fluorescents are way cheaper per lumen to buy,
Low-pressure sodium gas discharge lamps can be up to 29% efficient vs. roughly 14% tops for (actual shipping) LED bulbs and fluorescent tubes, but you wouldn’t want that color of light in your house.
Here’s another way to figure it out. As far as I can tell, it’s mostly LED lighting in their refrigerator and freezers, and “daylight harvesting” elsewhere, where they control skylights and dim the (standard) fluorescents when it’s nice and sunny.