One thermostat can control multiple air conditioners, the only limitation is the optical visibility of the transmitter (Smarther AC with Netatmo) and receivers (air conditioners). You need to test it properly to verify what is feasible. Note: If a Smarther AC with Netatmo controls multiple air conditioners via the built-in IR, all air conditioners must be the same model from the same manufacturer. They will all be set to the same settings.