Besides replacing standard incandescent bulbs with CFLs, you can save even more energy by installing ENERGY STAR® certified outdoor fixtures that use motion sensors or a photocell that turns on lights only at night.

Skill Level: Advanced
Outdoor lighting using these advanced technologies can be found at most home improvement and lighting stores. And many CFLs will fit into existing outdoor fixtures.
Cost Range: $15-$4,150
ENERGY STAR fixtures and bulbs pay for themselves over time in energy savings and longer bulb life.
Savings: Varies
Outdoor lights are some of the most frequently used fixtures in a home, so this is a good place to start saving energy. Just look for the ENERGY STAR label on products or packaging.