When it comes to energy savings, few upgrades pay off as quickly as a programmable thermostat. If you turn down the heat 5 degrees at night and 10 degrees during the day when no one is home, you’ll cut your energy bill by 5 to 20 percent. If you raise the temperature the same amount during the cooling season, your savings will be similar. You can do this with a manual thermostat, but a programmable model never forgets to turn down the heat at night and it can raise the temperature before you get out of bed in the morning.
Home centers carry several programmable models ranging from $25 to $100. Generally, more money means more programming options. Standard programmable thermostats sold in stores work with most heating/cooling systems, new or old. But there are exceptions: Electric baseboard heat systems require a “line voltage” thermostat that’s connected to much larger wires than we show here. Heat pumps often require special thermostats, too. If you can’t find the one you need at a store, search online. Before you shop, measure the “footprint” of the old thermostat. If you buy a new one that’s at least as large, you won’t be left with wallpaper gaps or paint to touch up.
Your old thermostat may look different from the one we show, but removing it will require similar steps. Turn off the power at the main electrical panel by switching off the furnace breaker. If the furnace circuit isn’t labeled, switch on the heat (not the air conditioning) and turn off breakers until the furnace stops. Remove the old thermostat (Photo 1). Chances are, it has a small glass tube containing mercury, which is toxic. Call your city or state environmental or health department for disposal instructions.
You’ll find anywhere from two to six wires connected to the old thermostat. If any of them aren’t connected to the screw terminals, you won’t connect them to the new thermostat either. The terminals are labeled with letters. As you remove each wire, label it to match the terminal using the tags included with the new thermostat (Photo 2). Disregard the color of the wires. When you remove the last wire, clip a clothespin to the cable so it can’t slip inside the wall.
Mount the wall plate (Photo 3). In most cases, you’ll simply connect the wires by matching labels to the letters on the new wall plate, but check the manufacturer’s instructions to be sure. Program and install the thermostat (Photo 4). Don’t forget to turn the power back on at the main panel.