An electrically operated aerosol-generating system includes a liquid storage portion configured to hold a liquid aerosol-forming substrate; an aerosol generator configured to receive liquid aerosol-forming substrate from the liquid storage portion; one or more capillary wicks configured to transfer liquid aerosol-forming substrate from the liquid storage portion to the aerosol generator; a first temperature sensor configured to sense the temperature of liquid aerosol-forming substrate held in the liquid storage portion; and electric circuitry. The electric circuitry is configured to monitor the temperature of the liquid aerosol-forming substrate held in the liquid storage portion as sensed by the first temperature sensor and determine depletion of liquid aerosol-forming substrate based on the temperature of the liquid aerosol-forming substrate.