In most cases, yes, you can use a smart thermostat with your existing heating and cooling system. However, it is important to ensure that the thermostat is compatible with your system before installation. Some older heating and cooling systems may not be compatible with newer, more advanced thermostats. Additionally, if you are unsure about the compatibility or installation process, it is recommended that you hire a professional HVAC technician to ensure the thermostat is installed correctly and functioning properly.