Use a programmable thermostat, which will let you choose temperatures and set on and off times for the day. That way you can heat your home when you're there but not when you're at the office. You won't have to remember to turn down the heat when you leave the house (or remind your kids or spouse to). And it could help you save hundreds on heating and A/C bills. By lowering your heating setting by 10 degrees for eight hours a day (while you're at work, for instance), you can shave as much as 15 percent off your bill. The Honeywell CT-3200 thermostat (shown) lets you set one schedule for weekdays and another for weekends. The fancier CT-3600 ($100) allows different on-off settings for each day of the week. Installation is virtually foolproof.