A coffee machine with a single boiler has only one boiler that is used for both brewing espresso and steaming milk. This means that the same boiler has to switch between the lower temperature required for brewing espresso and the higher temperature needed for steaming milk. As a result, there can be a delay between brewing espresso and steaming milk, as the boiler needs time to adjust to the different temperatures.
On the other hand, a coffee machine with dual boilers has separate boilers for brewing espresso and steaming milk. This allows the machine to maintain consistent temperatures for both processes simultaneously, without the need for switching between temperatures. As a result, coffee machines with dual boilers tend to offer faster performance and more consistent results, especially in high-volume environments where speed and efficiency are important.
In summary, the main difference between a coffee machine with a single boiler and one with dual boilers is the presence of separate boilers for brewing espresso and steaming milk in the latter, which typically leads to improved performance and consistency.