With an estimated annual savings of $100 and an initial outlay of only about $50, few upgrades pay for themselves as quickly as this one can. With a programmable thermostat, you can automatically adjust your heating and air-conditioning systems to match your family's seven-day-a-week schedule.
During the winter, for example, you can set it to turn off the heat after everyone's snug in bed, switch it back on in time for a warm wake-up, then putter along at a lower temp until the kids get home from school. The most advanced models let you program up to four settings for each day of the week. For every degree you lower your thermostat for an 8-hour period, you cut energy use by about 1 percent. Set it back 10 degrees overnight, and that's a 10 percent savings right there. And we bet you won't even feel the difference—except when you're paying the bills.
Honeywell RTH8500D 7-Day Touchscreen Programmable Thermostat: