9. Seal up drafts: If you live in an old house or apartment building, buy draft stops to slide under exterior and basement doors and windows. Energystar.gov estimates that proper insulation could cut heating and cooling costs by 20 percent.
10. Install a dimmer switch: This project is easier than it sounds and could save you hundreds of dollars in electricity costs (learn how at allyou.com/dimmers). Save even more by using compact fluorescents (CFLs) made for dimmers.