Thermoblock machines heat the water as it is used, similar to the way water is heated in a shower. This makes them smaller & much cheaper than a conventional boiler. The vast majority of budget coffee machines (below £200) will have thermoblocks. There is a wide range available, some with one thermoblock, some with two, some with a thermoblock AND a boiler. Some single thermoblock machines allow you to heat the water for espresso, then immediately for steam, then back again for another shot of espresso. For steam, the water passes through more slowly thereby reaching the higher temperature needed.
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