This type of espresso machine utilizes a single boiler to heat water for both brewing espresso and steaming milk. This means the machine must switch between brewing and steaming temperatures, requiring a short wait between tasks. A common example is a thermoblock machine which rapidly heats small amounts of water on demand.
These compact machines offer an entry point into espresso making, often at a more accessible price point than dual boiler models. Their smaller footprint makes them suitable for kitchens with limited counter space. Historically, this simpler design was the standard, paving the way for more complex machines as technology advanced. While the single boiler system presents a workflow challenge, it effectively delivers the core functionality of espresso brewing and milk steaming.