Espresso machines work with different technology: the one and the two-circuit system. The main difference is that dual circuits have separate circuits for brewing and steam generation, while single circuits have one unit.
Single circles are for pure espresso drinkers who only occasionally need steam to froth milk. The machines are equipped with a small boiler in which the water for the brewing process is heated. In the same boiler, the water is heated to produce steam, but this requires higher temperatures and the boiler must then be vented each time. Only when the water has cooled down again is the machine ready for the next espresso. The preparation of several cappuccinos or café lattes one after the other is correspondingly tedious. In addition, the water has to be heated again for several brewing processes.
In a two-circuit system, one water circuit is used to heat the water for the brewing process and one to generate steam. It is therefore possible to prepare espresso and froth milk at the same time, without the water having to cool down in the meantime and the boiler having to be vented. Also, the temperature in the kettle remains more stable during the brewing process than with the single circle. The latter is due to a larger volume of water and the construction of the double circuit. So when preparing multiple espresso drinks, especially with frothed milk, the dual circuit is faster than the single circuit.
