If your home’s current HVAC system is without a C or common wire and you have to replace the thermostat, you might wonder whether there are state-of-the-art smart thermostats that don’t need a C wire. Or do you have to rewire your system to add a C wire?

There are thermostats that don’t need a C wire to work. Many modern thermostats work with a C wire but are designed to also work without the wire if needed. Generally, they come with a power adapter that makes it possible. Most brands such as Nest, Ecobee, Wyze, and Honeywell nowadays offer thermostats that can work without a C wire. 

In this article, we list nine thermostats from seven well-known brands that can work without a C wire and briefly give the most important features of each.  

1. Nest E and Nest 3 Generation Thermostats

Nest 3rd Gen thermostat

Nest E thermostat

Nest is a world-renowned company making thermostats. They currently offer two excellent thermostat models, namely Nest 3 Generation (in short: Nest 3) and Nest E. Nest 3 is a full-featured thermostat compatible with 95% of the HVAC systems in the US and  Nest E is a budget, trimmed-down version, compatible with about 85% of the HVAC systems.


C wire is not necessary

In most HVAC systems both thermostat models will work without a C wire. Thus, you can use the Nest thermostats if your setup is currently without a C-wire.  Although, if there is a C wire already in place in your system, you just have to install the Nest thermostat and it will work.

Use a power adapter

It is however recommended that if you don’t have a C wire in your current setup, you use a C wire adapter. An adapter will ensure that the thermostat will never run into power and unexpected turning-off issues.

Special features

These two thermostats offer various features. Let’s look at two of the special features.

Self-learning feature

Both these Nest smart thermostats are “self-learning.” This means they learn your living habits and patterns in your home and then re-adjust the set schedules automatically when needed.  This feature gives high energy savings and the thermostat can pay for itself within 2 or 3 years of installation. 

Wi-Fi and Voice options

The Nest thermostats offer Wi-Fi connectivity so that you can control them from anywhere via the Internet. You can also interface extra temperature sensors (room sensors) with them. Voice control and smart home integrations like Apple Homekit, Google Home, and Amazon Alexa are enabled in these Nest thermostats.

2. Ecobee 3 Lite and Ecobee 4 Thermostats

Ecobee has two excellent smart thermostat models available, namely the very popular Ecobee 4 and the somewhat cheaper Ecobee 3 Lite. Both models offer features like built-in Amazon Alexa for voice control, geofencing, an extra room sensor, and Wi-Fi capability. Ecobee claims that you can save on average 23% of energy utilization every year. Within 2 to 3 years the thermostat has paid itself. 


C Wire Requirement

Although Ecobee thermostats work well with C wire connections, you can also use the Ecobee 3 Lite and Ecobee 4 if you don’t have a C-wire in your home electrical circuit. 

Power Extender Kit (PEK)

They both come with a PEK (Power Extender Kit) that you can use in homes without a C wire. With Ecobee all you have to do is to connect the PEK to the control board of your HVAC system. You can connect it to the furnace or heat pump. 


Ecobee thermostats are known for their compatibility features. Hubs that both thermostats can integrate with include Amazon Alexa, Apple HomeKit, Google Assistant, Samsung SmartThings, and Microsoft’s Cortana. 


With these two Ecobee thermostats you have different options to control the HVAC system.  

Both touchscreen and remote control

You can control your Ecobee thermostat by using the thermostat’s touchscreen. But you can also control the thermostat via Wi-Fi on your smartphone or tablet from anywhere in the world. 

Both models come with a mobile app which you can install on your smartphone to control the device from anywhere if your thermostat is connected to the internet via Wi-Fi

Voice control

The Ecobee 4 is equipped with built-in voice control features. Because Amazon’s Alexa is built into Ecobee 4 you can talk to the device from anywhere inside your home. The thermostat comes with a high sensitivity microphone to capture your voice easily. 


The Ecobee 4, is “self-learning” and can program itself after analyzing your family’s living habits and patterns. 

3. Mysa Thermostat

Mysa smart thermostat
Mysa Thermostat and App

Mysa is a line voltage thermostat exclusively designed for line voltage heating systems, including baseboard heaters, radiant ceiling heaters, fan-forced heaters, and convectors. The installation doesn’t need a C-wire. 

Mysa is the best Wi-Fi-enabled smart thermostat for line voltage systems. It can be controlled via the internet and has a user-friendly mobile app. 

Features of the Mysa thermostat

The Mysa thermostat offers a wide variety of features. We’ll look at the most important ones:


The thermostat has built-in humidity and temperature sensors. They predict the amount of humidity and temperature of your room and help the thermostat to maintain the room temperature.

When the temperature sensor measures the room temperature and finds it far from the set value, the power is reduced as the room temperature approaches the set value.

Its remote sensors sense the outside temperature when integrated with a smart hub like IFTTT through the Mysa app on your mobile.

Customized comfort and self-learning

You can control the Mysa thermostat on your mobile device from anywhere through the Mysa app. A total of 56 temperatures can be set for the whole week.  You can set the temperature and schedule according to your routine.

If you have a fixed routine at your home, the Mysa thermostat learns the routine and implements the temperature needs automatically.  And if you need to change the temperature in a particular zone in your home, you can use the “Hold indefinitely” option to override the set temperature.


The Mysa thermostat is compatible with most of the line voltage heating systems in your home, including 

  • an electric baseboard heater,
  • convectors (short cycle),
  • fan-forced convectors (long-cycle),
  • radiant ceiling heating, and 
  • self-contained hydronic baseboards.

4. Wyze Smart Wi-Fi thermostat

WYZE Smart WiFi Thermostat for Home with App Control Works with Alexa and Google Assistant, Black

Wyze has expanded its portfolio of affordable smart home devices to include smart thermostats. With their Wi-Fi-enabled Wyze Thermostat, you can control your home’s HVAC system from your phone or with voice commands.

Installation with an adapter

The Wyze Thermostat does not run on battery power, and therefore a C wire, also known as a “common” wire, will be ideal for power. However, if you don’t have a C wire you can still use the Wyze thermostat. Wyze provides a power adapter that you can use and when installed, your thermostat will work perfectly. 

Important features

Control from the app 

You can dial in the perfect temperature for your home from anywhere in the world with your mobile device. This can save energy and money, and prevent frozen plumbing.

Works with voice assistants 

The Wyze thermostat is compatible with voice hubs. You can, for instance, adjust the thermostat with your voice by asking Alexa. The thermostat is compatible with Alexa and Google Assistant. 

7-Day scheduling 

You can create daily schedules for every weekday and weekend. 

Zero learning curve temperature control 

Guests and family members can adjust temperatures easily. 

Easy DIY installation 

You have a step-by-step installation guide in the Wyze app.

Geofencing and movement detection  

You can set the thermostat to go into either heating or cooling mode when the connected camera detects motion. You can also use the geofencing feature to enable the home or away mode based on your mobile’s location.

5. Honeywell Home T9 Wi-Fi Smart Thermostat

With the Honeywell T9 smart thermostat which works with smart room sensors, you can adjust the temperature from anywhere and stay comfortable in the rooms that matter. You can place sensors in the rooms where you want to see and control the temperature and humidity. But the thermostat can also create an average temperature across the whole home.

Installation with an adapter

The T9 thermostat can work with or without a C wire. If you don’t have a C wire in your current HVAC system, you can still use the T9. You only have to utilize the C- wire power adapter that comes with the thermostat. Thus, it’s fully compatible with homes without C wires.

Important features

Let’s have a look at some of the important and handy features of the Honeywell home T9 Wi-Fi smart thermostat. 

Comfort control

The T9 senses the temperatures in the places that matter most and focuses on the rooms you choose by setting a schedule. The sensors can also be set to respond automatically to your lifestyle.

Room Sensors

The T9 allows you to place smart room sensors around your home. This enables you to see each room’s temperature and humidity. The sensors reach up to 200 feet to increase the quality of signal and data sent to the thermostat.

Easy control

You can control the T9 by using the Honeywell Home app or through Amazon Alexa, Apple HomeKit, Google Assistant, and other hubs.


The T9 is compatible with forced air (gas, oil or electric), hot water and steam, and heat pumps with electric backup.

Monthly energy reports

You’ll receive monthly energy reports regarding your heating and cooling trends. The thermostat will offer tips on reducing energy use. 

6. GE Cync Smart Thermostat

The programmable Cync smart thermostat is Bluetooth and Wi-Fi enabled. It is also compatible with Google Assistant and Alexa. The Cync smart thermostat displays a lot of information, but the Cync app is even more convenient to use. The app shows amongst many other things the current and set temperatures, and also indicates whether your HVAC system is in cooling or heating mode. 

Install with an adapter

The Cync thermostat can work with or without a C wire. Thus, you can use the thermostat even if your home’s HVAC is not equipped with a C wire.  You only have to install the C wire power adapter that comes with the thermostat. With the adapter, the thermostat will work perfectly. 

Important features

Voice control

The Cync thermostat allows you to turn up the heat or cool it down in any room in your home with voice control from anywhere in your house. You can activate voice control with Amazon Alexa or Google Assistant because the thermostat is compatible with both. 

Control with the Cync app

You can also control the thermostat out-of-home with the Cync app. The control via the app is easy and no hub or bridge is needed. You can change the temperature in your home remotely at anytime from anywhere. 

Compatibility and additional sensors

 The Cync thermostat is compatible with most heating and cooling systems: It is a thermostat that virtually can control any HVAC system. The thermostat also supports an optional sensor that you can install in a second room. This sensor helps your HVAC system to eliminate hot and cold spots in your home. The Cync can even accommodate more than one extra sensor. 

With these extra sensors, the Cync smart thermostat averages the temperatures at the thermostat, and in each room that has a sensor, and the HVAC system comes close to delivering your target temperature throughout your entire home.

7. Lux Geo Thermostat

The Lux Geo thermostat has been one of the first Wi-Fi thermostats that although it can work with a C wire doesn’t require system power if a C wire is not available. It is a 7-day programmable thermostat featuring a free iOS and Android app with geo-fencing. The thermostat can work with any of its 3 power options: 2 AA Lithium batteries, C wire, or micro USB. 



The Lux Geo thermostat is compatible with Amazon Alexa and Google Assistant. It is also compatible with most conventional HVAC systems. 

Geo app included

The Lux Geo thermostat comes with a related Android or iPhone app, including a geofencing feature. 


The thermostat is easy to program from the thermostat itself or the app. You can program it for up to 7 days and you can set the temperature to either Celsius or Fahrenheit. It also offers built-in geofencing. In other words, you save more money because the thermostat shuts down the devices if your mobile device moves out of the set surroundings of the home. 


If you have to install a new thermostat but your HVAC system and home are not wired with a C wire, there are quite a few thermostats you can choose from. You will also find that most modern state-of-the-art C wire thermostats come with a power adapter enabling you to install them without a C wire.  


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