Programmable thermostats adjust the temperature setting just as people do manually, but with greater efficiency. They can be set to turn on the furnace before you get up or return from work. In addition, they can be set for different schedules on different days; the most elaborate models, coupled with duct controls, can sense the

The number of cycles per day also varies. Two cycles a day are generally enough; however, if a large number of people enter and leave the house, or if you need heat for only brief periods in the morning and evening, four cycles per day will provide additional savings.

heat is various rooms and keep them at different temperatures.

When you shop for a programmable thermostat, make sure the thermostat is compatible with your heating system (and cooling system, if you have one). Most will work with forced-air, hot-water, radiant heat, and steam systems.

Go through the programming steps before you buy, Some models take as long as half and hour to set; others may require you to wait until the time of day coincides with that on the thermostat clock before starting the program.

Program schedules vary. Same include the same schedule for every day; others offer two schedules, one for the weekdays and the other for the weekends. Some have three schedules, one for the weekdays, one for Saturdays, and another for Sundays. Still others can be set for a different program each day.

Programmable thermostats should always have a manual override, so you can turn the heat on without having to reprogram the thermostat. A toll-free number or website support is another plus, especially for models with a complicated programming process.

Most simple programmable thermostats can be installed in about an hour with a screwdriver, drill, and a knife or wire-stripping tool. The thermostat wiring carries low-voltage current, which is quite safe.

Turn off the power to the furnace or air conditioner at the breaker panel and disconnect the appliance if possible. Some furnaces have separate switches or fuses or cords that can be disconnected.

Read the manufacturer's instructions and follow them if they differ from this sequence. Remove the old thermostat. Label the wires. Wrap the wires around a pencil or similar object to keep them from falling into the wall.

Clean the ends of the wires with steel wool. There should be about 1/2-inch of exposed conductor at the end of each wire. Position the base of the thermostat so the wires can come through. Connect the wires to the correct terminals, then attach thermostat cover and controls. Program the thermostat according to the manufacturer's directions.