Thermoblock vs Boiler: How the Heating Differs
A boiler holds a tank of heated water. A thermoblock holds almost none, and heats water as it passes through. Most of the differences you'll notice come from that one choice.
What you'll need
- Your manual, to find out which heater your machine has.
- A clear idea of what you want to know: warm-up, steam, or steady temperature.
The sections below take those three in turn.
The core difference
A boiler is a vessel of water kept hot. A thermoblock replaces that reservoir with a spiral-shaped tube threaded through an aluminium block.1
Wikipedia makes the same point about tankless heaters in general. They don't retain any water internally except what's in the heat exchanger coil.2
Warm-up
A heater with little water to warm gets there sooner. One guide names the relatively short heat-up time as the major advantage of a thermoblock over boiler machines.1
A boiler has more water to bring up to temperature. How long that takes depends on the model, so use the figure in your manual.
Steam and switching modes
Brew water and steam need different temperatures. On a machine with one boiler used for both jobs, Wikipedia says there's a warm up period between the espresso pull and the milk frothing.3
Another guide (kaffeemacher.de) says a single boiler must first be brought back down to brewing temperature before further shots.1
Other boiler layouts exist:
- A heat exchanger machine keeps its boiler at steaming temperature. It needs a cooling flush of 4 to 6 seconds before the first espresso pull.3
- A true dual boiler machine gives stable brew temperatures and fast steaming, but is larger and more expensive.3
Side by side
| Question | Boiler machines | Thermoblock machines |
|---|---|---|
| Where is the hot water? | Held in a heated vessel.1 | Heated as it flows through a tube.1 |
| Warm-up | Depends on the model. | A relatively short heat-up time.1 |
| Switching to steam | Depends on the layout. Some need a warm up period.3 | Covered on the steam switching page. |
| Brew temperature | Dual boilers are described as stable.3 | Depends on tube, length, flow and power.1 |
Which one suits which job
Neither design is better in every way. They trade one thing for another.
Wikipedia describes dual-boiler machines as stable, and says a single boiler needs a wait when it switches between brewing and steam.3 One guide describes a thermoblock as having a relatively short heat-up time.1
Reading your own manual
Makers don't all use "boiler", "thermoblock" and "heater" the same way. Look for a heating system description near the start of the manual. Trust that over any general rule.
For the flow-through side in detail, read the water's path from pump to cup.
Cited material
- Espresso machine systems explained (single boiler, thermoblock, dual boiler), kaffeemacher.de
- Tankless water heating, Wikipedia
- Espresso machine, Wikipedia
What Is a Thermoblock in an Espresso Machine?A thermoblock is a flow-through heater. See what's inside it, what it does in your machine, and where to check which heater your model has.
How a Thermoblock Heats Water as It FlowsFollow the water from the tank to the cup. See what the pump, the tube and the heated block each do, and why flow speed changes the result.
Why Thermoblock Machines Warm Up QuicklyOne maker's manual gives a heat-up time of under a minute, and thermoblocks are described as having a relatively short heat-up time.