Alternatively, you can screenshot your wiring diagram before you disconnect the Nest from the wall. Open the Nest app, tap the Settings cog in the upper-right corner, then select Equipment > Wiring.

Wiring adapter included: No; sold separately for $25 at Amazon, Best Buy, and Google. The fourth-generation Google Nest Learning Thermostat earns one of the top spots in our smart thermostat ratings.

The Cync Smart Thermostat costs $120 and will be available this month at Amazon, Best Buy and Lowe's. The Cync Temperature Sensor, which tracks the ambient temperature of other parts of the house ...

2. Pop Off the Faceplate You’ll need to remove the faceplate of your old thermostat to get at the low-voltage wiring and backplate. It should pop right off with a little bit of effort.

The wiring may also be switched for your fan settings. If you're comfortable doing so, you can try to switch the G wire, which controls the HVAC fan, with the Y wire, which often controls cooling.

Verify that your heat pump thermostat wiring is properly attached, according to the wiring diagram. “Make sure the wires are tight and all the way in the new thermostat,” Sherman says.

Most thermostat makers now have at least a single entry in the smart-home category, with some already on their second- and even third-gen products. All are vying to provide consumers with smarter ...