Best smart thermostats that don’t require a C wire 2021

Our top pick for the best smart thermostat without a C wire goes to the Nest Thermostat E. Its display simply shows the temperature setting, while the app lets you prioritize certain rooms’ cooling, change settings when you’re away, and lets you know if it senses a problem. Most importantly, the Thermostat E features a built-in rechargeable lithium-ion battery that bypasses the C Wire requirement. So if you can still find it in stock, this minimalist thermostat remains a reliable, affordable option.

ecobee’s 5th-gen smart thermostat builds upon everything that made its predecessors great — it supports up to 32 room sensors, with a great display and compatibility with most smart assistants. What’s new? It adds built-in Alexa voice controls with impressive built-in mics and a speaker, so you can easily change the temperature with a few words. The fifth-generation model doesn’t need a C wire, but it does come with a power extension kit that you’ll need to wire to your furnace control board.

The rare smart thermostat that’s compatible with 120V–240V, electric baseboard, and fan-forced heaters, the Mysa Smart Thermostat can mostly be installed yourself in a few minutes, is compatible with Alexa, Google, and HomeKit, and has all the smart tools you need to cut down on your energy usage: App scheduling, geofencing to track when you’re away from home, pre-heating or pre-cooling based on your schedule, and in-depth energy reports for possible improvements.

The Nest Learning Thermostat remains one of the smartest and useful thermostats today, supporting multiple zones, learned schedules, Alexa/Google Assistant integration, and HVAC monitoring. However, you may encounter power cycling issues if you install this without a C Wire. Google has released a new Nest Power Connector as a C Wire substitute for consistent power, but it won’t work for every home. All Nest Thermostats are good enough to risk testing without a C wire, but keep the receipt just in case.

The newest Nest is another thermostat that can work without a C wire, but in our Nest Thermostat review, we ended up having to wire one in. It’s entirely dependent upon whether your R and Y wires reach the voltage necessary to power everything; otherwise, your Nest Thermostat will shut down certain features to ensure the core temperature control still works. If your HVAC is fully compatible, it’s a versatile and affordable machine that uses geofencing and motion tracking to detect when you’re not home, saving you plenty of money. Otherwise, try installing the new Nest Power Connector and see if that solves your issues.

The ecobee 3 lite misses a few convenience features that the 5th-gen has, like a built-in occupancy sensor and built-in voice control. However, it’s an excellent budget option, and you can still fully control your home’s heating and cooling from anywhere in the world through the app or in your home with smart assistant devices. The ecobee3 lite also comes with the power extension kit to circumvent the need for a C wire.

If you don’t mind a bit of a dated look and lack of a 24/7 light-up display, then Emerson’s Sensi smart thermostat is your best budget pick. It only requires a C wire for heat- and cool-only systems (or heat pumps), and it still has full Wi-Fi connectivity, a straightforward app, easy program controls, and minimal setup required.

C wire aside, some of you may not even have central air but will still want to manage the climate throughout your home. For that, the Sensibo Sky controls your window or mobile AC appliances, letting you set up conditioning or heating schedules or pick specific temperatures through wifi monitoring. Plus, it makes your AC units controllable through Echo or Google Home commands.