An aerosol-generating system, a cartridge for an aerosol-generating system and a method of determining the amount of liquid aerosol-forming substrate held in a liquid storage portion of an aerosol-generating system. The aerosol-generating system comprises a liquid storage portion (201) for holding a liquid aerosol-forming substrate, a first electrode and a second electrode (322, 324) spaced from the first electrode, aerosol-generating means comprising one or more aerosol-generating elements and a control system. At least one of the aerosol-generating elements comprises one of the first electrode and the second electrode (322, 324). The first electrode and the second electrode (322, 324) are arranged such that at least a portion of the liquid storage portion (201) is arranged between the first electrode and the second electrode (322, 324). The control system is configured to measure an electrical quantity between the first electrode and the second electrode (322, 324) and determine the amount of liquid aerosol-forming substrate held in the liquid storage portion (201) based on the measured electrical quantity information.
