An aerosol-generating system includes a plurality of cartridges and an aerosol-generating device. At least one cartridge of the plurality of cartridges includes a first aerosol-forming substrate, the plurality of cartridges are configured for selective connection to each other to form a cartridge assembly. The aerosol-generating device includes a storage including a second aerosol-forming substrate in the storage, an electric heater configured to heat a portion of the second aerosol-forming substrate from the storage section during use of the aerosol-generating system, and a power supply housing, the power supply housing including a power supply and a controller, the controller configured to control a supply of electrical power from the power supply to the electric heater, the aerosol-generating device being configured to receive the cartridge assembly at a downstream end of the aerosol-generating device.