In this video blog post we cover the Best C Wire Transformer that we have tested and know works with the Nest Thermostat. This C wire Transformer will work with both the Nest Thermostat Generation 3 and the Nest Gen E Smart Thermostat.

How A Nest Thermostat Works

A C wire or Common wire transformer is use to power Nest Thermostats that are showing low power or low power errors. In most cases the addition of C wire transformer can fix the power error on the Nest Thermostat.

In the video below we teach you the easy way to install a C wire transformer. Adding a C or Common wire as it is also known provides your Nest Thermostat with a continuous source of power so that the internal battery inside the Nest Thermostat can charge.

In most cases the Nest Thermostat doesn’t need a c wire because it is able to charge the system, from being connected to the thermostat wires. But some HVAC systems don’t allow for enough current to pass through the Nest Thermostat while the HVAC system is off which causes the internal battery on the Nest to deplete. Once the battery is depleted the Nest Thermostat will no longer work unless charged from a the power port on the back or provided a continuous source of power like a common wire.

If your HAVC system puts out enough power for the Nest you won’t need to worry about the internal battery going dead and the nest turning off.

Less than 20% of HVAC systems need a common wire when installed with Nest but if you have a common wire it’s a good idea to connect it.

You’ll typically know either right away or within a few days if your Nest Thermostat needs a common wire as the thermostat will display a low power error message. Once you’ve seen the error message it’s time to install a C wire transformer to correct the issue.

Best C Wire Transformer

C Wire Transformer Fyve 24V Transformer

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.

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.

If you find that you need a C wire or C wire transformer you can either go through the steps we list here or just use the simple solution of adding a C wire transformer.