Check out this guide, and get motivated
If you come home after dark, or like using your yard when it's dark out you probably have some light fixtures outside (or fumble through the yard a lot). These fixtures can drain power, particularly if you need them to be on when you come home. Also, these fixtures can't use CFL bulbs in a lot of climates because the cold will wreak havoc with them.
Solution: An outdoor light that charges from the sun during the day and comes on automatically at night.