Invest in a programmable thermostat and set it way up or down (when everyone's at work/school, and asleep at night); program it to turn "on" shortly before folks get home/wake up/

Save: If used properly, as much as $150 a year.

Bigger picture: If every U.S. household turned the thermostat down by 10 degrees for seven hours each night during the heating season and seven hours each weekday when no one's home, the energy savings would prevent nearly 36 billion pounds of greenhouse gas emissions (roughly equal to emissions from 10 million cars).

If just 1 in 10 U.S. households bought Energy Star labeled heating and cooling equipment, the change would keep 18 billion pounds of greenhouse gas emissions out of the air (the equivalent of taking 1.5 million cars off the road).