How to Install a Programmable Thermostat

Save money on energy

Save a lot of money! Learn how to remove your old thermostat and install a new programmable thermostat—with no rewiring required.

By the DIY experts of The Family Handyman Magazine

TIME

Instant!

COMPLEXITY

Simple

COST

$20 - $100

Installation

You can reduce your home's heating and cooling costs by about 15 percent with a programmable thermostat. It automatically keeps the temperature at a comfortable level when you're home, but switches to an energy-saving level when you're away or asleep. Programmable thermostats are available from home centers and hardware stores. The higher-priced models provide more programming options.

Programmable thermostats will work with most gas or oil furnaces and central air conditioners. However, heat pumps, electric baseboards, and a few other systems require special features. Read the package to make sure the programmable thermostat you buy is compatible with your heating and cooling system. If you're unsure, call your local utility or a heating and cooling contractor.

Remove the old thermostat as shown in Photo 1. If your old thermostat contains mercury, you'll see a small glass tube with a shiny silver ball inside. Mercury is toxic. Take this type of thermostat to a hazardous waste disposal site.

There will be anywhere from two to five wires hooked up to the old thermostat. Label the thermostat wiring with marking tabs using the letters on the old screw terminals as reference. If your new thermostat doesn't come with marking tabs, use masking tape.

Clip a clothespin to the cable so it doesn't slide down inside the wall cavity, and mount the new wall plate (Photo 2). If the thermostat has back-up batteries, insert them before wiring the new thermostat (Photo 3).

The thermostat may need to be configured to your heating system. It may also come preprogrammed, but to maximize savings, set it up according to your schedule. Consult the instructions that come with the thermostat for system adjustments and programming. You won't save energy if the thermostat isn't programmed correctly.

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Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • Cordless drill
  • 4-in-1 screwdriver
  • Level
  • Drill bit set

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

  • Clothespin
  • Tape
  • Wall anchors