One spec line, and the morning it describes
Somewhere on every espresso machine's page is a word for how it heats water: thermoblock, thermocoil, single boiler, heat exchanger, dual boiler. It reads like trivia and it is the line that decides whether the machine makes two drinks in a row or asks you to stand and wait between them.
There are three arrangements underneath those words, and this page is what each one is and what each one holds. What one boiler does across a whole session, once the waiting starts, is brew temperature and what a single boiler holds.
The block and the coil, where the water is heated on its way through
A thermoblock is a lump of metal with a channel bored through it and a heating element cast into it. A thermocoil is the same idea drawn out as a tube. In both, the machine holds almost no hot water at all: cold water enters, travels the channel, and arrives at the group hot because the metal it just passed through was hot.
What that buys is speed. There is no tank to bring up, so the machine is ready in seconds rather than minutes, and it costs almost nothing to leave off until you want it. What it gives up is reserve. The hot water is only ever the water currently in the channel, so a long steam demand or several drinks back to back are asking the element to keep up in real time rather than drawing down a store.
The single boiler, where the water is held hot in a tank
A single boiler is a vessel, usually brass or stainless steel, holding a body of water at temperature. It brews from that water and steams from that water, and the two jobs want very different temperatures, so the machine sits at one and is switched up to the other.
What that buys is stability and reserve. A tank of hot metal and hot water does not flinch at a single shot. What it gives up is time, in one direction and then the other: up to steam after the shot, and back down before the next one. That waiting is the whole of the single-boiler experience and it is the subject of the page linked above.
The heat exchanger, where one boiler does both at once
A heat exchanger is the trick that removes the wait. The boiler is held at steam temperature, hot enough to make steam on demand, and a separate tube of fresh brew water runs through the middle of it. The water for the shot is heated on its way through, exactly as in a thermoblock, but by a boiler already sitting at steam heat rather than by an element switching on. Steam and coffee become available at the same time, from one boiler.
A dual boiler does the same thing with two vessels instead of one, holding each at its own temperature, and is the arrangement most commercial machines use.
What the fifteen machines on this site state
This site lists maker figures for fifteen espresso machines, and the boiler type, read on 6 September 2026, is one of two figures with no gap in it: every machine states it, and the tank volume now does too, since the last two Breville machines picked up a stated figure.
Nine of the fifteen name a block or a coil. One is stated as a thermoblock, insulated and single, with PID control, and eight are stated as thermocoils, several of them badged ThermoJet with a three-second heat-up. Five name a tank: a stainless steel single boiler, a lead-free brass one, a brass boiler of 250 ml, a brass boiler of 0.3 l with a ring brew group and a rotary valve, and a brass coffee boiler of 0.3 l. One names a dual boiler in stainless steel with PID control.
Not one of the fifteen names a heat exchanger there. One names it elsewhere. The Oracle Touch's own product page, read on 10 September 2026 for the maker specification sweep, states a dedicated steam boiler with an integrated heat exchange beside a dedicated espresso boiler, which is the arrangement described above doing its work inside a dual boiler rather than instead of one. No machine here uses a heat exchanger the way the section above describes, as the single vessel serving both jobs at once, and the moment one does its boiler-type line will say so.
The Bambino, the Stilosa and the Classic Pro
The Bambino is at the coil end. Its maker states a ThermoJet heating system that reaches extraction temperature in three seconds, which is the block-and-coil bargain stated as a headline: no wait to start, and no reserve behind it.
The Stilosa is the most honest machine here about how thin these lines can be. Its maker states a 15 bar pump and a stainless steel boiler, and that is all: the page names the metal and the vessel and does not say thermoblock, thermocoil or heat exchanger anywhere. It is carried here as a single boiler in stainless steel because that is what the page states, and adds nothing.
The Classic Pro is the tank at this end of the market. This site carries it with a brass boiler and group head across the current Classic line, which reaches this site as a description of the line rather than a sentence read off the maker's own page for this exact model, and it is written here as the shape of the machine rather than as a measured statement. The same machine is carried with a three-way solenoid valve and a removable tank in the 2 to 2.1 litre range, which arrives here the same way and is written with the same caution.
Reading the line before buying
Ask what the morning looks like rather than which word is better. One person drinking one milk drink is well served by a coil: on in seconds, off after, no reserve needed. Two people, or one person making two milk drinks in a row, is where the arrangement starts to cost something, and a tank held hot is worth its warm-up.
Speed to first shot and steadiness across four shots are different virtues, and no machine here has both. That is the trade the spec line is really printing.
