Automatic espresso machines are the most common commercial machines in cafés today. They can be programmed for different sized espresso servings and the flow of water is stopped automatically. These machines require skilled operators.

Fresh, cold water is pumped into the espresso machine. The water is heated, then forced under pressure through carefully ground and packed coffee grinds.

Hot water is also required to create steam for preparing milk for milk-based espresso beverages such as cappuccinos and flat whites.

The water temperature required for steaming milk is hotter than for extracting espresso so espresso machines have:

• two boilers set at different temperatures; or

• one boiler and a heat exchange unit

A heat exchange unit produces heated water by passing cold water through the hot water in the boiler.

Basic operation of a double-boiler espresso machine

Basic operation of an HX espresso machine (single boiler)

The following diagram shows the external parts of an automatic espresso machine: