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Why does a Smart Thermostat require a C-Wire?

A smart thermostat needs a constant flow of electricity from the furnace to keep the components with its circuit running. While old dial thermostat did not need any power to function, modern smart thermostats are more complex devices equipped with:

  • Wifi and Bluetooth connectivity
  • Multiple Sensors temperature and humidity sensors
  • Color Displays

New technologies and better consumer products have given us more practical and easier to use options when it comes to temperature control for our homes. Smart thermostats today are really quite smart! They can access the outside and inside temperatures, and takes those factors, as well as many others into account when trying to achieve our preferred indoor temperatures. Through their wifi connection, the smart devices can get access to local weather data on your home’s location even use artificial intelligence to make better decisions.

It’ll come as no surprise that with their new sensors and features, the newest smart thermostat models are more efficient than the older ones. One specific innovation. which this article focuses on is the power source. The most common source of power today is the common wire, more commonly called the “C-Wire”.  Although very popular among manufacturer, it is not possible for everyone to install these c-wire thermostats. In the upcoming paragraphs, we’ll cover some of the best no C wire smart thermostats that work without common wire.

Previously, there were many smart thermostat solutions that ran on batteries available on the market. Unfortunately for some consumers, the last decade has seen this low-voltage source of power evolve and become preferred choice for the majority of new thermostat coming to market. For a while it was nearly impossible to run a thermostat without C-wire or batteries. Every manufacturer was making thermostats that ran on C-wire or batteries.

It’s clear that this choice in the design of the new products was motivated by the additional stability of this solution. It is not as easy to smoothly run a smart thermostat without C-Wire. Without a C-Wire power can momentarily drop causing the charging to stop and sometimes the whole system to stop as well. In any case, to keep the smart thermostats up and running, you will need a thermostat that can use an alternative source of power. There are few modern systems which allow you to not need a C-Wire and which are far better than older thermostats that ran on cells/batteries. 

One new method developed by some manufacturers allow modern thermostats to get power from the hot and cold wires that bring power to your heating appliances. Essentially, while the circuit is closed and power is running through the heating system batteries within the system can charge. When ideal indoor temperature is reached and the power to the heaters is cut, the thermostat uses the power within the charged battery cells to keep functioning. These battery operated wifi thermostats are energy-efficient and only require a fraction of the power to run compared to old thermostats.

Before jumping into the article, we recently publish a Honeywell wifi thermostat review. Please consider this budget-friendly thermostat when making your purchase decision.

You might also like a fun blog posts on the Most Commonly Used Alexa Thermostat Commands!

How to Check if Your Thermostat has a C Wire?

To make a long story short, all you need to do is detach your old thermostat and verify whether a C wire can be found. Thermostats with C-wires will have one terminal with the name “C” next to it. If you do not find it, it’s also possible that your old thermostat did not need the C wire and that the wire was simply not pulled. Check your furnace for a C wire hiding behind the wall

Before buying a new thermostat, make sure to complete the previous checks on your home’s HVAC system. Buying a smart thermostat that is not compatible would certainly lead to a complicated installation and additional costs.

Are Power Adapters an Alternative to the C-Wire?

smart thermostat without c wire
HAUTURE C wire adapter 24 Volt Transformer

Yes, these systems are in fact an alternative to the C-wire. They can provide a source of power if you are using a smart thermostat that does requires a C-wire in a house that doesn’t have the C-wire. The power adapter simply plugs into a standard power outlet and can convert 110V/220V power to the low voltage equivalent of the C-Wire. Many manufacturers already include power kits in their standard package in case if your old system is not using c wire or not installed.

In my opinion, this is not the ideal solution. Not only does it take up a power outlet in your home, but it also not great to have a long wire go down your wall. Finally, if you don’t have an outlet near your thermostat location this solution doesn’t work.

If you can purchase a wifi thermostat that doesn’t require c wire, it will not only look better but will also be a simpler overall solution for your home. In this article, I list 2 of the best available thermostats that work without c wire, which are both WiFi-connected and include many practical smart features.

Best 3 Smart Thermostat No C Wire of 2021

Google Nest 3rd Gen Learning Thermostat

smart thermostat no c wire

Google Nest 3rd Gen Learning Thermostat is among the most feature-packed smart thermostats available on the market. It appeared a few years ago and has since seen many upgrades so that Google is now building the product’s third-generation. It’s equipped with powerful features, a gorgeous multi-colour display and in our opinion a fun futuristic look. This is the only thermostat in the market that works without C-Wire and is compatible with most new heating and cooling system.

This thermostat usually gets its power through the hot and cold wires. Given that we couldn’t find an exact compatibility list, if a power cycling issue arises, it will always be possible to setup this thermostat with a power adapter.

One key differentiator of this product is its AI-based learning. According to Google, this feature allows the thermostat to improve its efficiency overtime. The Google Nest 3rd Gen thermostat takes outdoor and indoor temperature readings and finds the most comfortable and cost efficient way to reach your desired temperature settings.

Some additional smart features includes custom temperature settings for each person in the home, as well as multiple room sensors that can all centralize their temperature readings to a single thermostat.

Shop now at Amazon

Lux Products GEO-WH Wi-Fi Thermostat

The Lux GEO-WH Wi-Fi Thermostat is a more simple product, yet it offers all the minimum features we expect with modern smart thermostats. At its lower price point (99$ as of writing this article)  it is among the best cheap smart thermostats without a c wire requirement.

As is the case with many large smart thermostat manufacturers, Lux Products has its own Android and Apple app to control temperature settings and is compatible with Amazon Alexa. One this advantage is that the Amazon Alexa feature only functions when the thermostat is connected by C wire. The cause is most likely the high power requirements, which aren’t feasible when the thermostat runs on batteries.

Overall, the minimalist design lower price point make this smart thermostat a very interesting option for systems that don’t have a c wire.

Shop now at Amazon

Ecobee SmartThermostat with Voice Control

wifi thermostat no c wire

The Ecobee Smart Thermostat with Voice Control is another amazing product that works without a C-wire. It can use as a power source both lithium batteries and an electrical outlet using a power adapter included in the box. Given the available power source options on this device, it is one of the most versatile smart thermostats, which should work in any new or old home.

It has other notable features, such as its ability to function with up to 32 room temperature sensors and built-in compatibility with Amazon Alexa. This opens the door to using some if this thermostat’s unique voice command features.

In addition, using the Ecobee app, allows you to gain access to many features. These include:

  • Remote access to all thermostat settings
  • Implement energy-saving temperature schedules
  • Connect to additional Ecobee devices, such as lights, cameras, alarm systems

According to the manufacturer, the smart features of this device can save you up to 23% on heating and cooling bills in a year.  Don’t forget that these elegant little devices will also add a level of style to your home.

Shop now at Amazon

Final Thoughts

I recommend you choose the option that fits your most important criteria. Are you looking for the best looking smart thermostat, the cheapest smart thermostat or the one with the most features? Once you’ve decided what’s important for you and properly established that you need don’t have a C-wire review the above products and make your pick.

Despite the many no C wire options available, it is usually possible to use a smart thermostat that requires a C wire a power outlet. With an additional 10 to 15 dollar power capable, you can also use any other smart thermostats available on the market.

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