How to Replace Your Thermostat

A homeowner adjusting the settings on a digital thermostat.
  • 4-8 hours
  • Intermediate
  • 100-300
What You'll Need
New thermostat
Needle-nosed pliers

Working around electricity can make anyone a little anxious, and some homeowners might get nervous if they need to replace a thermostat. Fortunately, replacing your thermostat is a fairly easy task to accomplish, and the savings and efficiency of your HVAC are well worth the effort.

Step 1 – Prep

Make sure the new thermostat is compatible to your 110-volt housing circuitry before you purchase it.

Step 2 – Switch Off the Power

Always turn off the electricity to the home thermostat at the power panel or circuit breaker box. Once you’ve located the correct circuit breaker and have switched it off, place a piece of masking tape over the switch so no one will turn it back on during your replacement installation process.

Step 3 – Remove Old Unit

Remove the old unit by snapping the cover off or unscrewing it if is attached by a set of screws. Pull the unit away from the wall and slide it off the mounting plate. Be careful not to damage the wires.

Step 4 – Disconnect Wiring

Remove the electric power supply wiring from the back of the thermostat. To prevent the wires from falling back into the wall, wrap them around a pencil so they can’t fit through the entry/exit hole. If the wires are not color-coded to the new thermostat, mark each one, noting the terminal they were attached to. Then, remove the mounting plate.

Step 5 – Attach New Mounting Plate

Place the mounting plate for the new thermostat against the wall in the same spot as the old one. Now, pull the wires from the wall through holes in the back of the new plate, and screw the plate into the wall. Make sure it is square to the wall and adjust the unit for leveling before tightening the mounting screws.

Step 6 – Connect Wires

When connecting the wires, make sure the green wire is connected to the terminal marked “G” or the same color. This operates the furnace fan blower. The white wire goes to the “W” marked terminal to operate the heater while the “Y” is for the yellow wire that connects to the air conditioner. If the wires were not color-coded, make sure to follow the labeling you created, and do not cross wires. If in doubt, call a professional electrician.

Step 7 – Mount on Mounting Plate

Place the unit on the mounting plate by sliding it into place. Turn your power back on and check to see if your new thermostat is working properly. Follow the manufacturer’s instructions for setting up the LED display panel that gives you access to temperature control and you’ll be set to go.