How to Connect Thermostat Wiring. Putting in a digital thermostat helps control your heating and cooling bill and maintains a more even temperature throughout your home. You can buy thermostats at a local hardware store and, in about an hour, you can improve your home's energy use.

Step 1

Turn off power to your thermostat. Not all thermostats have a power supply. For example, non-digital or battery-operated thermostats don't have power supplies. You can flip the breaker for the room if you are unsure.

Step 2

Remove the face plate of the old thermostat and unscrew it from the wall.

Step 3

Mark all wires before you remove them from the unit. You can do this by writing the corresponding letter on masking tape and taping the wire to the wall. Color-coded wiring doesn't always work with new thermostats, so label them carefully.

Step 4

Match your labeled wires to the new unit and attach them in the right places.

Step 5

Mount the back plate to wall. If the new thermostat is a different size from the old one, you must drill new holes. Make sure that the new holes are level to prevent any errors in the thermostat operation.

Step 6

Install new batteries if needed and program the thermostat.

Step 7

Check the thermostat with a level. It must be level to work correctly.