How to Install a Nest Thermostat
Safely replace an existing thermostat with a smart Nest unit, connect 24V HVAC control wires to the base plate, mount the display, and run app setup.
- Read the tools, materials, safety notes, and steps below for free.
- Tap Start Camera Coach when you want hands-free voice help.
- Allow camera and microphone. Point your phone at the work; the coach watches your progress and tells you the next step.
🧰 Required Tools & Equipment
- ✓ Phillips screwdriver
- ✓ Flathead screwdriver
- ✓ Non-contact voltage tester
- ✓ Smartphone with Google Home app
- ✓ Wire stripper
📦 Materials & Supplies
- ✓ Nest Thermostat and base plate
- ✓ Mounting screws and wall anchors
- ✓ Wire label stickers or masking tape
- ✓ Trim kit plate (optional)
⚠️ Safety Checkpoints & Warnings
- • Shut off electrical power to the HVAC system at the main breaker panel before removing the old thermostat.
- • Verify the wiring is low-voltage (24VAC); do not connect Nest to high-voltage (110V/120V/240V) lines with thick wire nuts.
- • Verify zero power at the exposed wires with a non-contact voltage tester before touching any copper leads.
📋 Step-by-Step Guide (6 Steps)
Turn Off Power and Verify
Locate your home circuit breaker panel and switch off the breaker controlling your heating and air conditioning system. Return to the existing thermostat and adjust the temperature setting to confirm the system does not turn on. Remove the faceplate and use a non-contact voltage tester directly against the exposed terminals to confirm no power is present.
- • Old thermostat faceplate is removed with wires visible.
- • Voltage tester tip is held against terminal screws without lighting up or beeping.
- • Turning off only the AC breaker while leaving the furnace/air handler powered.
- • Skipping the voltage test assuming the breaker label is accurate.
Photograph and Label Existing Wires
Take a clear, well-lit photo of the existing wiring connected to the terminal blocks for future reference. Apply the provided sticker labels (or marked masking tape) to each individual wire matching the terminal letter it currently occupies (e.g., R, W, Y, G, C). Ensure you label the wire based on the terminal label, not just the wire jacket color.
- • Every connected wire has a legible label tag wrapped around its jacket.
- • Photo clearly captures the terminal letters and connected colored wires.
- • Labeling wires based purely on wire insulation color instead of the terminal letter designation.
- • Disconnecting wires before photographing the original layout.
Remove Old Baseplate and Secure Wires
Use a screwdriver to loosen the terminal screws and disconnect each labeled wire. Unscrew the old mounting plate from the wall and gently pull the wire bundle through the center opening. Wrap a pen or tape across the wire bundle so the wires do not accidentally slip back into the wall cavity.
- • Old baseplate is fully detached from the wall.
- • Wire bundle protrudes 3-4 inches from the wall opening, held securely.
- • Allowing the wire bundle to drop behind the drywall cutout.
- • Yanking wires forcefully and damaging the copper conductors.
Mount Nest Base and Connect Wires
Feed the labeled wire bundle through the center hole of the Nest base plate (and optional trim plate if covering unpainted drywall). Align the built-in bubble level on the base until centered, then drive the mounting screws into the wall anchors. Press the spring-loaded terminal buttons down and fully insert each wire into its corresponding lettered port until the button stays depressed.
- • Nest base plate is screwed flat against the wall with the bubble level centered.
- • Terminal buttons stay clamped down with 3/8-inch of clean copper inserted into each labeled port.
- • Leaving too much exposed bare copper outside the push terminal.
- • Failing to push the terminal button all the way down, resulting in a loose wire grip.
Attach Display and Restore Power
Tuck excess wire slack back into the wall cavity so the wires sit flush against the base plate. Align the Nest display unit over the base plate and press firmly until you hear and feel a distinct click. Return to the breaker panel and switch the HVAC power breakers back on.
- • Nest display sits completely flush against the base plate without gaps.
- • Display screen turns on, showing the Nest startup logo or setup prompt.
- • Forcing the display onto the base while wires are bulging out behind it.
- • Attempting app setup before turning main power back on at the breaker.
Configure App and Test HVAC Modes
Open the Google Home app on your smartphone, tap the add device icon (+), and scan the QR code on the back of your thermostat or setup card. Follow the on-screen prompts to connect to Wi-Fi, select your heating/cooling equipment, and run the built-in system test. Verify that warm air blows during heating test and cool air blows during cooling test.
- • App displays 'Setup Complete' checkmark.
- • Thermostat screen shows current room temperature and target setpoint.
- • Skipping the system test phase in the app.
- • Selecting heat pump settings for a standard conventional gas furnace system.
Credit: inspired by an original tutorial by Google Nest — watch the original on YouTube.
Don’t have everything?
- No Wire label stickers? Blue painter's tape or masking tape labeled with a fine-tip permanent marker
- No Non-contact voltage tester? Digital multimeter set to 200V AC range