High voltage systems typically have a thermostat that is labeled 120 V or 240 V, and has two thick wires with wire nuts. High voltage systems, such as electric baseboard heaters, aren't compatible with Nest thermostats.

Does Nest work with 240V?

Simply put, they are not compatible. It's also overly complex and dangerous. Nest and Ecobee thermostats were made to control low voltage (24V) heating systems and electric baseboard heating is high (or line) voltage (120V or 240V). ... The hardware isn't built for electric baseboard heating.

Is there a smart thermostat that works with high voltage?

The Sinope Smart Thermostat (TH1123ZB) is one of the best high voltage thermostats on the market, and it works on 240 Volts. The thermostat comes with great compatibility, and it works well with Amazon Alexa, Google Home, Samsung SmartThings, and Hubitat.