Our top-choice smart thermostats that don’t require a C wire in 2021 are…

Simple and straightforward

Nest Thermostat E

Staff pick

Our top pick for the best smart thermostat without a C wire goes to the Nest Thermostat E. It’s a great option for folks who don’t want to spend too much and prefer minimalist devices. The 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.

$128 at Walmart $169 at B&H

Some rewiring required

ecobee SmartThermostat (5th Gen)

ecobee’s 5th-gen smart thermostat builds upon everything that made its predecessors great (up to 32 room sensors, great display, plays nice with all the smart assistants) by adding built-in Alexa voice control and a speaker. Like its ecobee brethren, 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.

$249 at Amazon $250 at Best Buy

For high/line voltage systems

Mysa Smart Thermostat

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.

$139 at Amazon $140 at Best Buy $139 at Home Depot

Proceed with caution…

Nest Learning Thermostat (3rd Gen)

Nest’s Learning Thermostat remains one of the smartest and useful thermostats today, supporting multiple zones, learned schedules, Alexa/Google Assistant integration, and HVAC monitoring. It also doesn’t need a C wire, though some users have discovered power cycling issues that may or not be an issue for you without a C wire. It’s good enough that we’ll recommend risking a purchase regardless.

$230 at Amazon $250 at Best Buy $223 at Walmart

Check your voltage

Nest Thermostat

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.

$130 at Best Buy $130 at B&H $130 at Staples

Best brand, lowest cost

ecobee3 lite

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 that lets you circumvent the need for a C wire.

$169 at Amazon $170 at Best Buy $169 at Home Depot

Middle of the road

ecobee4

If you want to save a little money compared to the newest ecobee thermostat, the fourth-generation model is a nice mid-tier option. Like the ecobee SmartThermostat, it has built-in Alexa and works with Google Assistant and HomeKit, is compatible with remote room sensors, and has identical energy savings. You’ll just miss out on Alexa calling, Spotify connect, Bluetooth streaming, the 5.0 Wi-Fi band, and the newer model’s nice glass display.

$246 at Amazon $249 at Home Depot

Budget pick

Emerson Sensi Wi-Fi Smart Thermostat

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, with a straightforward app, easy program controls, and minimal setup required.

$94 at Amazon $100 at Home Depot $99 at Lowe’s

For standalone AC units

Sensibo Sky

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.

$119 at Amazon $119 at Walmart $120 at Lowe’s