This type of espresso machine utilizes a single boiler for both brewing espresso and steaming milk. A smaller tube, the heat exchanger, runs through the boiler, carrying brewing water. This water is heated indirectly by the surrounding boiler water, kept at a higher temperature for steam production. This design allows for near-simultaneous brewing and steaming, a significant advantage for busy environments.
The ability to brew and steam concurrently significantly streamlines workflow, making this system popular in cafes and restaurants with moderate espresso demand. This configuration presents a balance between cost and functionality, offering a more affordable alternative to dual-boiler systems while still providing the convenience of simultaneous operation. Historically, this system represented a significant step forward in espresso machine technology, enabling more efficient beverage preparation.