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Best smart thermostats that don't require a C wire 2022

Many of the best smart thermostats require a C wire ("common" wire) to provide enough power for LED displays and Wi-Fi-powered advanced functions. That's why some homeowners need smart thermostats without a C wire requirement. The thermostats below run on low power or ship with DIY power adapters that anyone can install. 

Here are our favorite picks that'll help you avoid hiring a professional to rewire your home — just keep in mind that some thermostats have more reliable performance without a C wire than others.

Ditch the professional and consider these smart thermostats

No C wire? No problem (mostly)!

The majority of older homes and heating/cooling systems won't have a C wire. Since you may not be comfortable installing the wire yourself or paying for an electrician, these smart thermostats without a C wire will still reduce your energy bills. Some use batteries that you'll have to keep replacing, while others require a power extension kit that will still necessitate some simple wiring on your part. Many of these are among the best smart thermostats, so you can rest assured that a C-wire requirement doesn't equate to better quality.

If you prefer a painless, battery-powered unit, the Nest Thermostat E is your best option — especially since it's so affordable compared to other thermostats. It has many smart features like motion and multi-room sensing, Google Assistant and Alexa commands, and an auto-away model. By this point, it's a relatively old thermostat, and Google has mostly moved on to the new Nest Thermostat. Still, as we broke down in our Nest Thermostat E vs. Nest Thermostat article, the old dog has a few tricks that make it a better choice.

Whether your Nest or Nest Learning Thermostat will work with a Power Connector varies from home to home. For more consistency, consider ecobee instead.

Plus, a Nest Thermostat — or an older Nest Learning Thermostat (3rd Gen) — demands slightly more power than the Nest E and may be compromised without a C wire as a result. Google has released the new Google Nest Power Connector to bypass the C Wire requirement, and it solved those issues for some people, but other reviewers report that their low power issues didn't go away even with the new Power Connector. So whether a Nest works without a C Wire may vary from one house to the next.

If you have a little electrical know-how (and a little extra cash), the ecobee SmartThermostat will require you to wire in a power extension kit to replace the missing C wire. Thankfully, ecobee designed them with DIY installation in mind, so the process shouldn't be too complicated. Once installed, it's the best smart thermostat for multiple zones, meaning it's great for people with large homes where rooms are unevenly heated. From its multiroom sensor integration to its built-in Alexa to control your entire home, ecobee's offering is truly the king of smart thermostats — and its price reflects it.

Or, if you're feeling bold, you can take the plunge and use a simple Venstar kit to install a new set of HVAC-compatible wires. With this tool installed, virtually any of the excellent smart thermostats available should be compatible with your home's heating and cooling.

Michael L Hicks
Senior Editor, VR/AR and fitness

Michael spent years freelancing on every tech topic under the sun before settling down on the real exciting stuff: virtual reality, fitness wearables, gaming, and how tech intersects with our world. He's a semi-reformed Apple-to-Android user who loves running, D&D, and Star Wars. Find him on Twitter at @Michael_L_Hicks.

With contributions from