"Boiler" gets used loosely to describe almost any heating system, but a true boiler stores a reservoir of hot water, and several popular machines don't work that way at all. Here's what's actually a boiler, what isn't, and which machines can brew and steam at the same time.
A single boiler machine heats and stores a reservoir of water, which it uses for both brewing and steaming. Since that reservoir can only sit at one temperature at a time, the machine has to compromise, either running slightly cooler than ideal for steaming or slightly hotter than ideal for brewing, or asking you to wait between the two.
A dual boiler machine uses two separate boilers, one dedicated to brewing and one to steam, each held at its own ideal temperature. This is what actually enables brewing and steaming at the same time without a compromise.
ThermoJet, Thermocoil, and Thermoblock are a different category entirely. These systems heat water as it flows through, on demand, rather than storing a reservoir at all. That's how they reach brewing temperature so quickly, but it also means they're not a smaller version of a single boiler, they're a fundamentally different way of heating water. Most of the machines covered on this site fall into this category, not into single or dual boiler.
| Machine | Boiler Detail | Brew + Steam Simultaneously | |
|---|---|---|---|
| Profitec Pro 300 | Separate brew and steam boilers | Yes | Check Price → |
| Lelit Bianca | Separate brew and steam boilers, notably larger than the Pro 300's | Yes | Check Price → |
| Machine | Boiler Detail | Brew + Steam Simultaneously | |
|---|---|---|---|
| Gaggia Classic Pro | Single boiler, shared between brew and steam | No | Check Price → |
| Rancilio Silvia | Single boiler, larger than the Gaggia's, shared between brew and steam | No | Check Price → |
| Machine | System | Brew + Steam Simultaneously | |
|---|---|---|---|
| DeLonghi Dedica | Thermoblock | No | Check Price → |
| Breville Bambino | ThermoJet | No | Check Price → |
| Breville Bambino Plus | ThermoJet | No | Check Price → |
| Breville Barista Express | Thermocoil | No | Check Price → |
| Breville Barista Pro | ThermoJet | No | Check Price → |
| DeLonghi La Specialista | Dual Thermoblock | Yes, by design | Check Price → |
Neither. ThermoJet, along with Thermocoil and Thermoblock, heats water on demand rather than storing a reservoir of hot water the way a true boiler does. It's a genuinely different category of heating system, not a smaller version of a single boiler.
Only the Profitec Pro 300 and the Lelit Bianca. Both use two separate boilers, one for brewing and one for steam, so they can do both at once without the temperature tradeoffs a single boiler machine has to make.
The La Specialista can, using a dual Thermoblock setup built specifically for that purpose. It's not a true dual boiler in the traditional sense, but it accomplishes a similar result through a different mechanism.
Not worse, just different. A single boiler like the one in the Rancilio Silvia or Gaggia Classic Pro holds a reservoir of hot water, which some enthusiasts feel gives more thermal mass and stability once it's fully warmed up, at the cost of a much longer wait to get there. ThermoJet and similar systems trade that thermal mass for a near-instant start.