Updated: Jan 2, 2019
Another bit of sage advice from DCSix!
Compact Fluorescent Lamps (CFLs) use 20% of the energy used by typical incandescent bulbs to give the same amount of light. A 22 Watt CFL has the same light output as a 100 Watt incandescent.
LED (Light-emitting diode) lights use less than 10% of the energy required for corresponding tungsten lights.
Low energy lighting will give highest savings in rooms that are most often used.