Readers like you help support MUO. When you make a purchase using links on our site, we may earn an affiliate commission. Read More.
Smart thermostats are incredibly convenient, allowing people to automate their home's heating and cooling system.
The ability to connect your home's thermostat to a Wi-Fi connection means you can control your smart thermostat from anywhere, even if you aren't at home. This not only allows you to schedule the right temperature for your environment but also helps you save costs on your energy bill. It's the perfect way to start building a smart home as many smart thermostats offer integration with other products like locks, cameras, and more.
When looking for the best smart thermostats, it's important to understand whether you need to purchase a smart thermostat with or without a C wire.
What Is a C Wire?
The C wire (common wire) powers a smart thermostat by providing a constant flow of 24 VAC (volts AC).
The term "constant flow" is the key here, because the C wire isn't the source of power. The R wires are the actual source of power, but they are not continuous, hence the use of the C wire.
However, not all home wiring consists of a C wire. The good news is, some of the best smart thermostats do not require the power from the C wire to work.
In fact, some of the best smart thermostats like the Google Nest Thermostat have no requirement for the C wire as they contain rechargeable batteries or other technology that removes the need for one. Here's a look at some of the best.
1. Google Nest Thermostat E
Google's Nest Thermostat E is a simple smart thermostat that uses a rechargeable lithium-ion battery. This bypasses the need for the C wire, offering an always-on display that details the current temperature setting.
Compatible with most voice assistants like Google Assistant and Amazon Alexa, the Google Nest Thermostat E can be adjusted easily using voice commands, or via the handy smartphone app.
From one simple dashboard, you can see how much energy you've saved, invite other family members to control the smart thermostat, and set temperature schedules in each of your rooms.
Best of all, the Google Nest Thermostat E is incredibly easy to install and is one of the most versatile Wi-Fi thermostats with no C wire.
2. ecobee Lite SmartThermostat
If you're searching for a smart thermostat that you can install without a C wire, on a budget, the ecobee Lite SmartThermostat is a wise choice.
While it doesn't feature all of the bells and whistles the latest generation ecobee does, it still allows you to control your heating and cooling directly from the app. This means you can schedule programs efficiently.
The ecobee Lite SmartThermostat ships with a Power Extender Kit that allows you to bypass the C wire requirement.
Aside from controlling your HVAC system, this smart thermostat is small and easy to install, making it a great option if you want to install a smart thermostat without a C wire.
3. Google Nest Learning Thermostat
Google's Nest Learning Thermostat is one of the most popular smart thermostats, and for good reason. It's a fully programmable thermostat that boasts voice controls, compatible with Alexa, and comes in a range of designs.
One of the added benefits of opting for the Google Nest Learning Thermostat is that it can be installed with or without a C wire. So if you move homes, you'll have both options available.
A word of caution, however, is that some users may experience issues with their HVAC systems due to the smart thermostat taking power from the furnace control circuits to charge up the internal battery.
In most cases, this won't be an issue, and you'll be able to enjoy your feature-rich smart thermostat without a C wire.
4. Sensibo Sky
For those that don't have a central heating system or want to control just their AC units, the Sensibo Sky is an excellent smart air conditioner system.
With quick and easy installation, the Sensibo Sky doesn't require a C wire to be able to control your AC units. You can connect the smart system via Wi-Fi to control it via the smartphone app.
Alternatively, use voice assistants like Apple's Siri, Google, and Amazon Alexa to control your home's temperature.
By leveraging the Sensibo Sky's smart features, you can save energy and reduce your bills with scheduling and geo-fencing.
5. Lux GEO-WH Wi-Fi Thermostat
While not the most stylish smart thermostat, the Lux GEO-WH Wi-Fi Thermostat is a safe bet if you've tried other smart thermostats without a C wire that aren't compatible with your heating system.
It can be powered via two AA batteries, micro-USB, or C wire. This gives you multiple options, making the process far more straightforward, and easy to install.
You can program your Lux GEO-WH Wi-Fi Thermostat via the unit or through the app with a Wi-Fi connection.
The only scenario where you would need a C wire for this smart thermostat is if you wanted to use its Alexa voice control capabilities.
6. Emerson Sensi
One of the most affordable smart thermostats you can install without a C wire is the Emerson Sensi Wi-Fi Smart Thermostat. It works with Alexa and boasts DIY installation.
For most applications, the C wire isn't required. You'll only need a C wire if you have a heat or cool-only system, heat pump, or you want to use Apple HomeKit.
Using Wi-Fi connectivity, the Emerson Sensi's dated style can easily be overlooked in favor of its easy controls, allowing you to program your home's heating from anywhere.
It's compatible with iOS and Android and displays usage reports so you can keep on top of your energy usage.
7. Mysa Thermostat
The Mysa Smart Thermostat stands out due to its mid-range price and its stylish design. This line voltage thermostat has been designed to work with line voltage heating systems like baseboard heaters, fan-forced heaters, and convectors.
A C wire is not required for installation, and, once installed, the Mysa Smart Thermostat boasts a good range of features, despite little information being displayed on the panel itself.
Built-in, there are humidity and temperature sensors; when connected to a smart hub, it can sense the outside temperature and adjust your heating accordingly. There are also scheduling functions, routines the thermostat can learn, and geofencing.
This smart thermostat is easy to install in a matter of minutes. And, as well as being able to control your heating via the app, it's compatible with Alexa, Google Assistant, and Apple HomeKit too.
8. Wyze Smart Thermostat
Like the Google Nest Learning Thermostat, the Wyze Smart Thermostat can be installed with or without a C wire. As it isn't battery-powered, a C wire would usually replace the power. However, without a C wire, you can use the power adapter that's included.
This thermostat works with the majority of heating systems, but you can use Wyze's Thermostat Compatibility Checker to be sure your system is compatible.
Using the app, you can control the Wyze Smart Thermostat wherever you are. This includes 7-day scheduling, home/sleep/away modes, usage tracking, and more. And, if you're away from home and have a guest housesitting for you, you can share the control with your guests through the Wyze app.
Thanks to the built-in motion sensor, this smart thermostat can be programmed to automatically turn on or off. Similarly, it can use your phone's location to detect if you're not at home.
9. Honeywell Home T9
The Honeywell Home T9 smart thermostat can work with or without a C wire. Similar to the Wyze Smart Thermostat, the T9 comes with a C wire power adapter that you can use in replacement of a C wire.
Compatible with room sensors that detect the temperature of each room, this smart thermostat can respond automatically to your schedule. You will be able to see each room's temperature and humidity, which you can see in the mobile app.
If you like to stay on top of the energy you're using, you'll get a monthly energy report along with tips on how to reduce your energy usage.
And although the Honeywell Home T9 is at the upper end of the price scale, it is incredibly useful and a long-term investment for your home. Plus, it's compatible with Alexa, Google Assistant, and Apple HomeKit, so you can say "Alexa, set the temperature to 72".
No C Wire—No Problem
Buying a smart thermostat that doesn't require a C wire for installation doesn't mean you're in for a poor experience.
In fact, some of the most advanced and popular smart thermostats like the Google Nest Learning Thermostat are among those that can be installed without a C wire.
Now it's easier than ever to keep an eye on your spending and control your energy usage using smart technology.
The good news is, some of the best smart thermostats do not require the power from the C wire to work. In fact, some of the best smart thermostats like the Google Nest Thermostat have no requirement for the C wire as they contain rechargeable batteries or other technology that removes the need for one.Is there a smart thermostat that works with 2 wires? ›
Both the Nest E and Nest Gen 3 Thermostats can be installed with 2 wires. The procedure to install the Nest thermostat with 2 wires is the same for both thermostats.Can I use Amazon smart thermostat without C wire? ›
Amazon Smart Thermostat requires a C-wire or a power adapter kit. Use the compatibility checker to see if your home has one already. Guided installation instructions are included in the Alexa app.Does smart thermostat need C wire? ›
With a Nest Thermostat E or Nest Learning Thermostat, you'll need to install a C wire if the thermostat has power issues or its battery often drains.What if thermostat has no C terminal? ›
While your thermostat may not technically need a C-wire to operate, it gets the power for its screen and Wi-Fi capabilities through “phantom power” or “power stealing.” Basically, this means your thermostat gets a kick of extra power whenever your HVAC system is running.How many wires do you need to install a smart thermostat? ›
Smart thermostats like Nest and Ecobee thermostats require 4 wire thermostat wiring to function properly. In addition to heating (2 wire thermostats) and C or fan (3 wire thermostats), 4 wire thermostats include the cooling wire, usually in blue or yellow color.Can you have 2 thermostats on one furnace? ›
Absolutely. One house can have two thermostats — the two thermostat units connect to one HVAC unit to make your home more comfortable by giving different zones a different temperature as desired. An HVAC professional will also install dampers and controls for better temperature regulation in those areas.Can I use ecobee without C wire? ›
Please download the ecobee app (available for Apple and Android devices) and follow the step-by-step installation guide. If you're lacking a C wire and have at least four wires at your thermostat to work with (refer to this article if you only have two wires), you'll want to install the Power Extender Kit (PEK).Does Honeywell require C wire? ›
Known as the common wire, (C-Wire) provides Wi-Fi thermostats continuous power from heating (e.g. furnaces) and cooling systems (e.g. Air Conditioning systems). C-Wires are required on all Resideo Wi-Fi thermostats.Can I install a WIFI thermostat without C wire? ›
As these smart thermostats run on a 24V AC supply, you can actually use a common doorbell power supply to provide power in lieu of a C-wire. This simply involves plugging the power adapter into the wall nearby and running the wires back to the thermostat, plugging them into the terminals for the C-wire as normal.
An extra unused wire in the wall can be used as the C wire for your new thermostat. The extra wire will also need to be connected to the C (common) terminal at the heating and cooling system. This will provide power to your new thermostat.What happens if you install nest without C wire? ›
In a system with a C-wire, the Nest charges itself from the C-wire's current and all is fine. In a system without a C-wire, though, Nest recharges its battery when the heating or cooling runs. It diverts a little bit of the power to itself and charges its own battery.Is the blue wire always the C wire? ›
Blue wires are also called C wires because they are the Common wire. C wires are necessary for any smart thermostat that needs to be connected to a power source 24/7, regardless of your heat pump type.Does Nest E require C wire? ›
The Nest Thermostat E is designed to work even if your home doesn't have a common (C) wire, but installing a new C wire may be required. If you have a dual fuel system, we strongly recommend professional installation.Can you replace any thermostat with a smart thermostat? ›
Do smart thermostats work with all homes? Strictly speaking, smart thermostats don't work with all homes, but they do work with the vast majority. You typically need a central HVAC system in order to be able to install a smart thermostat. Smart thermostats also require Wi-Fi and a smartphone for full control.What color is the C wire on a thermostat? ›
The C, or common wire, provides smart thermostats with continual power. It's usually blue, but it may also be black, brown or purple. The O or orange wire connects to your heat pump (if applicable).Can I just install a smart thermostat? ›
Learning how to install a smart thermostat can be a simple project, just make sure to keep thermostat compatibility in mind. It's important to first find a smart thermostat that's compatible with your HVAC system, so you can follow the right installation instructions.How do you wire a smart thermostat with 4 wires? ›
In general, the heating wire (often white), goes into the “W” port, the cooling wire (often yellow), goes into the “Y” port, the wire that sends power from the HVAC system to the thermostat (often red), goes into the “R” port, the fan wire (often green), goes into the “G” port, and the common wire (often blue), which ...How many wires does a Nest require? ›
How Many Wires Does Nest Learning Thermostat Need? Typically, four. This is parallel to the standard four wires that most standard thermostats use.Should upstairs thermostat be higher or lower than downstairs? ›
Upper stories are warmer than lower ones, so you want to adjust the temperature depending on the season to properly set up upstairs and downstairs thermostats. During the summer, set your upstairs thermostat to your desired temperature, and the downstairs unit two degrees warmer.
If you have multiple thermostats in your home, you can replace any or all of them with a Nest thermostat. You won't need to replace all of your current thermostats, they'll keep controlling your system just like they always have.How do I install multiple smart thermostats? ›
It can be done in three simple steps: Replace your existing thermostat with a smart multi zone thermostat (a thermostat with remote sensors). Purchase external sensors for each room and connect them to your smart thermostat via the app. Place a sensor in each room you'd like to control as a separate zone.Can I use RC wire as C wire? ›
The C and Rc wires are not the same. To install this thermostat you should follow the exact same wiring of the previous thermostat.Do battery powered thermostats use C wire? ›
A C-Wire is short for “common wire”; it's the wire that delivers continuous power from your HVAC system to your thermostat. Pretty much all the best smart thermostats or Wi-Fi-enabled thermostats require a C-Wire connection, since the C-Wire eliminates the need for separate batteries.Does T9 thermostat need C-wire? ›
Do I need a c-wire to install the T9 Smart Thermostat? No, the T9 Smart Thermostat comes with a c-wire adapter so it's compatible with homes that do not have a c-wire.Do most homes have C-wire for thermostat? ›
In today's electric market, most newer heating and cooling systems have C-wires, which guarantees compatibility for the installation of all smart thermostats. If you do not have a low voltage heating system, you will not have a C-wire.Does Honeywell t3 thermostat require C-wire? ›
This Honeywell programmable thermostat uses an internal disposable battery for its primary power. A "C" wire is not required.Is the C wire just a ground? ›
A: C stands for common. The common wire is the ground or negative wire. To complete the circuit that provides power to the thermostat you need a positive and negative wire from the 24V transformer.How do you identify C wire? ›
Blue wires are also called “C” wires because they are the Common wire. C wires are necessary for any “smart” thermostat that needs to be connected to a power source 24/7, regardless of your heat pump type. (It's important to determine that your heat pump is compatible with your thermostat before you decide.)What will replace copper wires? ›
Aluminum is just one-third the price and weight of copper, but it is only about 60% as conductive.
Nest thermostat connectors are built so that only one wire can be inserted into each connector. Putting more than one wire into a Nest thermostat connector can damage your system and your thermostat. Instead of using jumper wires, Nest Learning Thermostats use an internal jumper between the Rh and Rc connectors.Is ecobee better than Nest? ›
For the money, Ecobee has the better value. You get the integrated Alexa speaker and air quality sensor, as well as one included remote sensor with your purchase. In terms of features, accessories and overall options, Ecobee blows Nest away.Can you use Nest with baseboard heaters? ›
Electric baseboard systems are generally not compatible with Nest thermostats. They are only compatible if they're currently controlled by a 24 V thermostat.Can I install Sensi thermostat without C wire? ›
The Sensi Wi-Fi Programmable Thermostat works on most combined heating and cooling systems without a c-wire. The Sensi Smart Thermostat also works on most combined heating and cooling systems without a c-wire, however, will require a c-wire for Apple HomeKit functionality.Do most homes have C wire for thermostat? ›
In today's electric market, most newer heating and cooling systems have C-wires, which guarantees compatibility for the installation of all smart thermostats. If you do not have a low voltage heating system, you will not have a C-wire.Does Ecobee thermostat require C wire? ›
Your ecobee3 does not need them. Some thermostats do not have a C-wire. The C-wire is used to reliably provide power to the thermostat. In this case, the PEK can use the existing wires to power your thermostat.How many wires does a smart thermostat need? ›
Smart thermostats like Nest and Ecobee thermostats require 4 wire thermostat wiring to function properly. In addition to heating (2 wire thermostats) and C or fan (3 wire thermostats), 4 wire thermostats include the cooling wire, usually in blue or yellow color.Does Honeywell t4 require C wire? ›
A C wire is needed on almost all Honeywell Wi-Fi thermostats except the Smart Round Thermostat (earlier called Lyric Round). C wire stands for a common wire which connects the Wi-Fi thermostat with the heating and cooling systems to provide constant power to the smart thermostat.Do older homes have C wire? ›
The furnaces and air conditioning systems in many homes, especially older ones, tend to have four wires or fewer, and often exclude the C-wire altogether. My previous house had a four-wire configuration -- an R wire (for power), a G wire (for the fan), a Y wire (for AC) and a W wire (for heat).How much does it cost to run C wire? ›
The cost to install a C-wire will range from $120 to $200. A professional electrician will run the “common” wire from your furnace to your new smart thermostat. This requires fishing the new wires through your existing walls and making the connection at both ends.