Install a Smart Thermostat Yourself

Lower energy bills and a house that's the right temperature when you walk in. Easier than it looks — with one safety caveat.

How to build it

1. 1

   Check compatibility first

   Before buying, remove your old thermostat's faceplate and photograph the wiring. Most smart thermostats need a 'C' (common) wire — if you don't have one, choose a model with an adapter kit. The manufacturer's compatibility checker does this in minutes.

2. 2

   Kill the power

   Turn off power to your HVAC system at the breaker — not just the thermostat. These are low-voltage wires, but shorting them can blow the furnace control board fuse.

3. 3

   Label every wire

   Photograph the old wiring, then label each wire with the included stickers according to the terminal letter it came from (R, G, Y, W, C). The wire colors are hints, not rules — trust the terminal letters.

4. 4

   Swap the base plates

   Unscrew the old base, thread the wires through the new one, and connect each labeled wire to its matching terminal. Level the base before tightening — a crooked thermostat is forever.

5. 5

   Power up and configure

   Restore power, snap on the faceplate, and follow the app's setup. Run the system through heat and cool modes to confirm everything's wired right.