7 Best Smart Thermostats That Don’t Require a C Wire 2023 (Plus More Options!)

Numerous top-tier, name-brand smart thermostats need a C wire (common wire) to supply adequate power for LED screens, Wi-Fi, and other advanced features. However, older homes are often not wired with a C wire. As a result, many homeowners seek smart thermostats that don’t require a C wire. 

Yes, you can have a smart thermostat without a C wire!

The thermostats listed below either operate on low power or come with DIY power adapters that are easy to install. If you’re familiar with smart thermostats, you’ll notice that the thermostats listed are all the top-selling, most well-known thermostats. 

The manufacturers have found ways to make sure their products are available to everyone.

The following selections are our favorites that can help you bypass the need to have your home required. However, bear in mind that the performance without a C wire may vary among thermostats. The Nest is notorious for having problems with the internal battery dying.

Ecobee Premium Smart Thermostat

Ecobee Smart Thermostat Premium

Lastest & Greatest Ecobee Thermostat!

Uses Power Extender Kit (PEK)

If you don’t have a C wire and have a minimum of four wires available at your thermostat, you can use the Power Extender Kit (PEK). The PEK is installed at your furnace control board and is connected to your existing thermostat wires to generate a C wire. Installation is usually quite easy and straightforward.

Ecobee’s most recent smart thermostat enhances the features that made its previous models exceptional — it now supports up to 32 room sensors, has a stunning new larger display, and uses radar to detect occupancy

What sets it apart? The thermostat incorporates built-in Alexa and Siri voice controls, complete with high-quality microphones and a speaker, enabling effortless temperature adjustments using simple voice commands. Additionally, the thermostat comes with an integrated air quality sensor to ensure you breathe clean air.

Ecobee 3 Lite Smart Thermostat

Ecobee 3 Lite

Lowest Cost Ecobee Thermostat

Uses Power Extender Kit (PEK)

The Ecobee 3 lite lacks some of the convenient features found in the Premium model, such as an integrated occupancy sensor and built-in voice control. The Ecobee 3 Lite does still work with room sensors.

However, it serves as an outstanding budget-friendly choice, allowing you to manage your home’s heating and cooling remotely via the app or through smart assistant devices at home. 

Additionally, the ecobee3 lite includes a power extension kit to bypass the need for a C wire.

The Ecobee 3 Lite is what I personally use in my home, and it works great for my needs. 

Nest Smart Thermostat

Google Nest Thermostat

Lowest Cost Google Nest Thermostat

Uses Power Stealing

The latest Nest thermostat can function without a C wire; however, some customers eventually had to wire one in. 

The necessity of a C wire depends on whether your R and Y wires provide sufficient voltage to power all features; if not, your Nest Thermostat will deactivate certain functions to maintain core temperature control or display errors that are troublesome to solve. 

If your HVAC system is fully compatible, the thermostat is a versatile and cost-effective device that employs geofencing and motion tracking to identify when you’re not home, potentially saving you a significant amount of money. 

If you encounter issues, consider installing the new Nest Power Connector to see if it resolves the problem.

This Nest Thermostat also supports room temperature sensors now.

Nest Learning Smart Thermostat

Google Nest Learning Thermostat 

Lastest & Greatest Google Nest Thermostat!

Uses Power Stealing

The Nest Learning Thermostat continues to be one of the most intelligent and versatile thermostats available, offering support for multiple zones, adaptive schedules, Alexa/Google Assistant integration, and HVAC monitoring. 

The Nest Learning Thermostat uses power stealing, just like the previous Nest thermostat. 

However, installing it without a C wire may lead to power cycling issues, among other problems. 

Google has introduced a Nest Power Connector as an alternative to the C wire for consistent power, but it may not be suitable for all homes. 

It’s worth trying Nest Thermostats without a C wire, but be sure to retain the receipt, just in case.

Nest Power Connector

Nest Power Connector – Nest Thermostat C Wire Adapter

In case your Nest thermostat experiences power-related problems that restrict its capabilities, this power connector serves as a C wire substitute. Google’s instructional video demonstrates how to install it, or you can pay to have a professional install one.

Amazon Smart Thermostat

Amazon Smart Thermostat

Uses Power Extender Kit (PEK)

If your system doesn’t have a C wire, the Amazon Smart Thermostat can be purchased with a C-wire power adapter, which you can use as an alternative to providing the necessary power for the thermostat. The C-wire power adapter is what they call their version of the power extender kit.

The Amazon Smart Thermostat is an affordable and user-friendly smart thermostat designed to help you efficiently manage your home’s heating and cooling. It is compatible with popular voice assistants like Amazon Alexa, enabling you to control the thermostat using voice commands. 

With features like scheduling, energy-saving modes, and remote control through the Alexa app, it aims to simplify climate control and reduce energy consumption. Its straightforward installation process and compatibility with most HVAC systems make it an attractive option for homeowners seeking a cost-effective smart thermostat with essential features.

Mysa Smart Thermostat

Mysa Smart Thermostat

For high voltage (120V – 240V) HVAC systems

In rare cases where the smart thermostat is compatible with 120V-240V, electric baseboard, and fan-forced heaters, the Mysa Smart Thermostat can usually be installed by yourself in just a few minutes. 

It is compatible with Alexa, Google, and HomeKit, offering all the smart features necessary to reduce energy consumption, such as app scheduling, geofencing to detect when you’re away from home, pre-heating or pre-cooling based on your routine, and comprehensive energy reports for potential enhancements.

Lux Kono Smart Thermostat

Lux Kono

Uses Power Extender Kit (PEK)

If you don’t have a C wire and have a minimum of four wires available at your thermostat, you can use the LUX Power Bridge. The Power Bridge is what they call their version of a Power Extender Kit (PEK). 

The LUX Power Bridge is installed at your furnace control board and is connected to your existing thermostat wires to generate a C wire. Installation is usually quite easy and straightforward.

The Lux Kono is a sleek and stylish smart thermostat that offers a range of features to help you manage your home’s heating and cooling efficiently. It is compatible with popular smart home systems like Amazon Alexa, Google Assistant, and Apple HomeKit, allowing you to control the thermostat using voice commands. 

The Lux Kono also supports geofencing and provides energy-saving scheduling options to help reduce energy consumption. Its user-friendly interface and easy installation make it an attractive choice for homeowners seeking a budget-friendly smart thermostat with essential features.

I personally prefer the Ecobee interface over Lux, but I know not everybody will like the same things I like.

Sensibo Sky

Sensibo Sky – Smart Home Air Conditioner System

Make Any A/C Smart – Doesn’t have to be central 

Setting the C wire issue aside, some individuals may not have central air but still desire to regulate their home’s climate. 

In such cases, the Sensibo Sky can control your mini-splits or portable AC units, enabling you to establish heating or cooling schedules or select precise temperatures via Wi-Fi monitoring. 

Additionally, it allows you to control your AC units through Amazon Echo or Google Home voice commands, enhancing convenience and ease of use.


From personal experience with friends, family, and my own house, I recommend getting either a Nest or an Ecobee. 

Nest Thermostats might function in some homes without a C-Wire, but there’s still a possibility that additional power may be needed. 

Google introduced the new Google Nest Power Connector to circumvent the C Wire requirement, which resolved the issues for some users. 

However, other reviewers mentioned that their low power problems persisted even with the new Power Connector. Consequently, the effectiveness of a Nest thermostat without a C Wire may vary between different homes.

For those with some electrical knowledge (and a bit of extra budget), the Ecobee Smart Thermostat Premium requires wiring a power extension kit to substitute for the missing C wire. 

Fortunately, Ecobee designed the kit with DIY installation in mind, making the process relatively straightforward. Once installed, it becomes the top smart thermostat for multiple zones, making it ideal for large homes with unevenly heated rooms. 

From its multiroom sensor integration to its built-in Alexa for whole-home control, Ecobee’s thermostat is truly the pinnacle of smart thermostats — and its price tag reflects that.

In addition to temperature sensors that thermostats use, there are a lot of different types of sensors to learn about.


Hey, I’m Josh! Welcome to Expert Home Automation. Tech is what I do for a living and as a hobby. You can learn more about me here.

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