We’ve tested dozens of different transformers to power the Nest Thermostat and found that the 24V C wire transformer from Fyve was the Best C Wire transformer that worked with the Nest Thermostat. In our video blog post below we show you how you can install a C wire transformer.
If you want to look at other options for installing a C wire we have a complete Nest Thermostat C wire installation wire guide in another post that teaches you other more advanced options for connecting a C Wire.
Related Post: How to install a common wire the advanced guide
The vast majority of Nest Thermostat installations don’t require a C wire transformer so we recommend that you first connect your Nest Thermostat to your HVAC system and test it to see if it will work without a C wire.