How to Install a Programmable Thermostat

Use less energy on heating and cooling with this simple, inexpensive solution.

| April 17, 2008

Programmable thermostat

Programmable thermostats are a great investment. In the first year after installation, you can reduce your energy bills by more than you paid for the thermostat.


The Earth Day celebrations are over, and you’ve got an eco-hangover (just a little too much green for one day). What to do? Ease into your next green project: Install a programmable thermostat.

Replacing your old thermostat with a programmable model can reduce the amount of energy used to heat and cool your home by as much as 15 percent (if you’re not already adjusting your thermostat manually a few times each day). They’re super easy to install, and Energy Star ratings can help select the most effective models. Many programmable thermostats cost less than $90, so you’re likely to recoup your investment quickly in lower energy bills.

Before choosing a new thermostat, check how many wires are attached to your current one. The wires should be smaller than wires running to electrical boxes (like those of outlets and light switches). If they’re heavier wires, they carry higher voltage — so you’ll want to hire an electrician for the job. This is usually the case only if you have electric baseboard heat.

The Installation Process

Turn off the power to the furnace at the circuit box (or remove the fuse).

Remove the old thermostat, being careful to label each wire with a piece of masking tape as you remove it. There should be a letter near the place each wire was attached. Tape the wires to the wall so you don’t lose them inside the wall.

The new thermostat may have a template to help you mark the wall where screws will attach the thermostat. Or you may need to hold the base plate of the new thermostat against the wall and mark (with a pencil) the place you need to drill holes. Unlike thermostats that operate with mercury, leveling a digital thermostat isn’t necessary, but it looks better.

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