The espresso machine that meets your needs is the best fit for you. That sounds trivial, but it's actually crucial for determining which espresso machine is right for you.
Are you an espresso purist? Then a single-boiler espresso machine might be for you.
Are cappuccino and latte macchiato highly popular? Then a dual-boiler espresso machine quickly makes sense.
Those seeking maximum consistency and performance will be happy with a dual-boiler espresso machine.
In this article, we will highlight the differences between the various espresso machine systems: single-boiler, heat-exchanger, and dual-boiler. By looking at the strengths and weaknesses of each machine, it quickly becomes clear which espresso machine suits you best.
If you want to learn how to make espresso step by step, this tutorial with video will help.
How the Single-Boiler Espresso Machine works
A single water circuit runs through a single boiler in a single-boiler espresso machine. The boiler's job is to bring the water to the required temperature. For making espresso, the ideal temperature, depending on the coffee and roast, is between 90 and 96 °C.
Temperature is also needed to froth milk. To produce enough steam, the boiler temperature is heated to 120 – 130 °C. In a single-boiler machine, this must be done with the same boiler that also heats the brewing water.
After brewing an espresso, the single-boiler system increases the heating. This can be started manually at the touch of a button. The small, usually powerful boiler then heats up from the brewing temperature to approx. 125 °C. Once the target temperature is reached, frothing can begin.
Before further espresso shots, the boiler's temperature must first be brought back to the brewing temperature of 92 – 96 °C . We have explained this principle in detail using the example of the Rancilio Silvia.
Diagram of a Single-Boiler Espresso Machine
Temperature surfing a prerequisite for delicious coffee
Mastering the temperatures is a prerequisite for good coffee on a single-boiler espresso machine. Brewing temperatures of over 100 °C lead to a very unpleasant coffee taste. The coffee becomes very bitter and sour – both at an intensity level that you wouldn't want to drink.
If the steam pressure does not reach sufficiently high temperatures, you will not be happy with frothing. At low boiler temperatures, large amounts of water, instead of steam, are blown into the milk. This prevents the milk from frothing and simultaneously dilutes it more and more with water.
With single-boiler machines, it is therefore absolutely necessary to get to know your own espresso machine well in order to estimate the times between heating up and cooling down.
Does a single-boiler make good espresso?
Absolutely! The espresso from a single-boiler espresso machine tastes just as good as an espresso from an expensive commercial espresso machine. The prerequisite for this is that the temperature is right. And in the single-boiler price segment, this usually cannot be read externally. You have to learn to master the temperature. Or you can forgo the milk frothing function. Then the boiler does not have to function for both brewing and frothing and is often better set to the target brewing temperature.
Pros: What speaks for the single-boiler
- Makes very good espresso if the temperature is right
- Affordable machines on the market
- Relatively small models also available
- Can be heated up to froth milk depending on the model
- Due to the small boiler, it can heat up and cool down relatively quickly
Cons: What speaks against the single-boiler
- Is not self-explanatory. It requires some engagement with the machine to master it.
- Temperature management is required to achieve good beverage results.
- While the operation of the machine can be learned, for "espresso beginners" who already have a lot to learn, such as how to properly set the grinder and froth milk, this type of machine is not, in our opinion, the perfect beginner machine.
- Lack of temperature consistency due to the small boiler.
Who is the single-boiler suitable for? For espresso drinkers and milk frothers with nerves of steel.
Pro-Tip: If you like to tinker, you can retrofit many a single-boiler with a PID control. This promises high temperature stability and turns the single-boiler into a machine with high precision – unbeatable in terms of price-performance. We will explain how this works in a later post.
Examples of Single-Boiler Espresso Machines
Lelit Victoria PL91T, Gaggia New Classic, Bezzera Hobby, Lelit Grace PL81T, Lelit Anna PL41 LEM, ECM Classica PID, Bezzera Unica PID, Quick Mill Carola, Rancilio Silvia
How the Thermoblock Espresso Machine works
The thermoblock is an alternative to the boiler principle. Instead of a heated water reservoir, a spirally shaped tube is drawn through an aluminum block. A heating element runs along the tube. The water is heated as it passes through the tube. This process is equivalent to an instantaneous water heater.
The big advantage over espresso machines with boilers is the relatively short heat-up time. The heating element heats up quickly. The "block" can be brought to temperature quickly by making a few shots without coffee.
The temperature stability of the thermoblock depends on the installation of the tube, its length, the water flow rate, and the heating power. In well-tuned machines, this is relatively or even very precise in standard operation. Positive examples include machines from Ascaso or the Decent Espresso Machine.
Problems arise when a lot or a little coffee is brewed. When making many espressos or long drinks (Lungo, Café crème-like), the surrounding area cools down due to the large amount of cold water flowing through, and the water is no longer heated to a sufficient brewing temperature.
If the water flow is slow, e.g., due to very finely ground coffee powder, the water heats up beyond the target.
The larger the thermoblock, the better
In most smaller thermoblock espresso machines, the thermoblock is relatively small. In order to reach the desired target temperature during the short flow time, the block must therefore be heated significantly higher than the actual target temperature. This further exacerbates the described problem.
The larger the thermoblock, the closer the block's temperature is to the actual target temperature, and thus it can provide the desired temperature more consistently, even at higher or lower performance.
Thermoblock machines are generally not well suited for frothing milk. The pressure built up is relatively low. In addition, the foam produced has a relatively high residual moisture content, which dilutes the milk significantly. The pump sprays small amounts of water into the thermoblock to generate pressure, which then evaporates and creates pressure. Due to these bursts, the steam also exits the milk wand in bursts, which makes homogeneous frothing difficult. However, there are also positive counter-examples, such as the Sage Bambino Plus.
Pros: What speaks for thermoblock espresso machines
- Fast heating
- Depending on the construction and tuning, precise temperature and correspondingly good espresso
- Minimal limescale build-up
- Relatively inexpensive
Cons: What speaks against thermoblock espresso machines
- Temperature fluctuations depending on flow rate and water quantity
- Dependent on the size of the thermoblock
- Not well suited for frothing milk
Examples of Thermoblock Espresso Machines
Sage Barista Express, Sage Barista Pro, Lelit Glenda PL41, Quick Mill Peagso, ECM Casa V, Lelit Kate PL82T, Ascaso Steel Duo PID, Ascaso Dream PID, Sage Bambino Plus
Who is it suitable for: Penny-pinchers willing to compromise on quality
How the Heat-Exchanger Espresso Machine Works
Two water circuits after the pump characterize the heat-exchanger espresso machine system. A boiler is the central element. This is heated to a temperature of 120 – 130 °C. The steam pressure for milk frothing is taken directly from this boiler. In addition, a tube runs through the boiler, which transports the brewing water towards the espresso preparation.
The tube functions as a heat exchanger. As fresh water flows through the tube, which is surrounded by hot water, it heats up. The hot water in the boiler acts somewhat like a thermoblock here.
The material thickness of the tube and the "residence time" of the brewing water in the boiler are crucial for how much the brewing water heats up.
Diagram of a Heat-Exchanger Espresso Machine
Milk frothing is a joy with the heat-exchanger system
Heat-exchanger espresso machines are the favorites of all cappuccino drinkers. The hot boiler generates powerful steam, allowing you to froth milk and pull espresso simultaneously. This is a big difference from the single-boiler espresso machine, where you have time to meditate between brewing espresso and frothing milk. Temperature surfing is thus a thing of the past compared to a single-boiler.
The heat-exchanger also has enough power to brew several espressos in a row. Depending on the size of the boiler, a slight drop in performance can be noticed after 2 to 6 frothed milk pitchers. However, this is quickly overcome if you give the machine time to reheat.
Heat-exchanger and temperature consistency
Comparing the temperature fluctuations of the heat-exchanger with those of the single-boiler espresso machine, the difference is striking. But the heat-exchanger also has its "problems." The brewing water is heated by its residence time in the heat-exchanging tube. If no espresso is brewed for a longer period, the temperature of the brewing water corresponds to the ambient temperature. In other words, it is more than boiling hot. Therefore, flushing, i.e., a blank shot, is very important with heat exchangers. This removes the heated water from the tube, and the fresh water flowing in is already at temperature.
If you brew one espresso after another at a family celebration, there is a risk that the brewing temperature will fall below the 90 °C threshold. This leads to sour-tasting espressos and reduced extraction capability.
Pros: What speaks for heat-exchanger espresso machines
- Good espresso and frothing capability
- Simultaneous frothing and brewing is possible (large boiler)
- Good temperature consistency
Cons: What speaks against heat-exchanger espresso machines
- Machines for home use are not suitable for large parties or gastronomy. Neither the steam pressure nor the brewing water temperature can withstand this.
- More expensive than single-boiler and thermoblock machines
Who is it suitable for: Espresso lovers and cappuccino drinkers.
Options for Heat-Exchanger Espresso Machines
Espresso machines with a heat-exchanger system are available in many variations from numerous retailers. Of course, the machines each have certain advantages and disadvantages and different internal constructions, such as slightly larger or smaller boilers and a different aesthetic.
Two improvements to the heat exchanger are particularly noteworthy and affect both quality and price.
PID control
The PID control option regulates the brewing water temperature. You can read a good explanation here of how exactly it works. PID stands for Proportional Integral Derivative.
The PID control helps the espresso machine to heat precisely within its target range. The target range can be adjusted via a controller, although with heat exchangers, it should be noted that you are always changing the boiler temperature, which affects both the brewing temperature and the steam pressure. So, if the steam pressure is insufficient, the boiler temperature can be increased. However, this also increases the temperature that heats the heat exchanger, which, for example, can make longer blank shots or flushing worthwhile.
Rotary pump vs. vibratory pump
Another upgrade for the heat exchanger is the rotary pump. The rotary pump is more powerful and heavier. The rotary pump is quieter than the vibratory pump, which is useful depending on where the espresso machine is located.
Due to their robustness and power, rotary pumps are standard in multi-group commercial machines.
Examples of Heat-Exchanger Espresso Machines
Bezzera BZ10, Quickmill Rubino 0981, Bezzera Magica SMN, Bezzera Strega R AL, Profitec Pro 500, ECM Mechanika V, Elba 1 and 2, Rocket Appartamento, Lelit Mara X, Rocket Cronometro Mozzafiatto, Sanremo Cube
For a really good overview of the most important heat-exchanger models, check out our comparison of 12 heat-exchanger espresso machines.
Dual-Boiler Espresso Machine – Function and Application
No question, whoever invests in a dual-boiler buys temperature precision that shows itself with every espresso preparation. Two separate boilers deliver the desired temperature. The steam boiler brews at the desired 120 – 130 °C, and the brewing boiler precisely delivers the set brewing temperature between 90 and 96 °C.
Juggling temperatures comes to an end. The generally larger steam boiler is controlled to the appropriate pressure via a pressurestat. In the brewing boiler, a PID control precisely controls the brewing temperature down to a tenth of a degree.
Many dual-boilers also come standard with a rotary pump, which contributes to their durability in terms of power and robustness. Durability and consistency in brewing, that's what dual-boiler systems are known for. Even with a higher frequency of drinks, these devices rarely falter.
Diagram of a Dual-Boiler Espresso Machine
Consistency from shot to shot and during extraction
Quality from espresso shot to espresso shot is primarily demonstrated by reliability within the system. The crucial factors are temperature and pressure with each shot and within a single brew. The consistency during the brewing time is a factor that we have not yet discussed in detail with the other machine types.
There, the challenge was already to start the brewing with the same brewing temperature. Within a single shot, the temperature often fluctuates as well. This is because, for example, colder water flows through the heat exchanger, which in the second part of an espresso shot encounters less back pressure in the coffee puck than in the first part of the brewing.
The dual-boiler masters consistency here because it is supplied from a perfectly tempered water reservoir.
Froth milk until the stadium is served
Even if the Kelly Family is visiting, the milk foam will flow. And the best part: if we overdo it and empty the steam boiler to exhaustion, the espresso is not affected. This is the advantage of the independent boiler for both areas.
The steam pressure can be increased by raising the temperature in the steam boiler, and thus also the frothing speed. If you prefer to froth more slowly, you can reduce the pressure slightly. Here, too, the brewing temperature is not affected.
Semi-Professional Use
A single-group dual-boiler is suitable for small catering events, larger family gatherings, and, depending on the type, for continuous operation. Many machines of this type can also be connected to a fixed water supply, which is another advantage.
We regularly use our La Marzocco Linea, a Dalla Corte Mini, and of course a La Marzocco GS 3 for catering assignments. What we like about them is that, unlike commercial machines, these machines, built for household or office use, run on standard household current of 220/230 volts. This is a significant advantage depending on the location.
Of course, there are also significant quality differences between dual boilers, which we will elaborate on in our tests of the individual machines. For machines of the quality class of the La Marzocco GS 3, it can be said that they are also well-suited for a small cafe to start with. If the business is running well, another machine of the same type can be added, and you already have a two-group setup. If it's less busy, one of the two machines can already be cleaned and "closed down" (catering jargon).
Turn off the steam boiler and save energy
Sensibly, the steam boiler can be manually deactivated. This is useful when only espresso drinkers are present. This saves energy and protects both the environment and your wallet. For us, this is a decisive quality criterion for a dual boiler.
The size of the brew boiler is always a source of discussion. If it is too large, the brew water sits in the boiler unnecessarily long, is heated again and again, and is only slowly replaced. A larger boiler also takes longer to reach temperature. A larger boiler only makes sense if, for example, half the floor in the office drinks espresso during lunch break.
Pros: What speaks for dual boiler espresso machines
- Precise brewing temperature
- Brewing temperature and steam pressure independent of each other
- Consistency from shot to shot
- Consistency within a shot
- Suitable for semi-professional use (larger guest volume)
- Some models with commercial components are extremely robust and precise
Cons: What speaks against dual boiler espresso machines
- High-priced
- Dual boiler does not always mean PID and rotary pump. Be sure to read up on what else is installed in the machine.
Examples of dual boiler espresso machines
Profitec Pro 300 Dualboiler, La Spaziale Dream, Bezzera Duo Top MN, Quick Mill New Vetrano 2B, Rocket R58/Cinquantotto, Bezzera Matrix, ECM Synchonika Dualboiler, Dalla Corte Mini, La Marzocco GS/3, La Marzocco Linea Mini
Espresso grinder as a basic prerequisite
This article deals with the different types of espresso machines. However, a note on a quality grinder should still be placed here incidentally. As coffee makers, we repeatedly observe in both gastronomy and private households that the selection of the coffee grinder is not sufficiently considered. We have seen such absurd pairs as an espresso machine for CHF 7000/€ 6500 next to an espresso grinder for CHF 360/€ 290.
That's simply a shame. In such a setting, the grinder dramatically limits the quality of the espresso machine. When planning a budget for the purchase of an espresso machine, we advise reserving at least ¼, preferably 1/3, of the budget for the grinder. Unevenly ground coffee extracts inhomogeneously and ensures that the quality of your espresso is limited.
Conclusion - Which espresso machine is right for you?
| Thermoblock | Single Boiler | Heat Exchanger | Dual Boiler | |
| I only drink espresso! | xx | xx | xxx | xxxx |
| A cappuccino once in a while is fine. | x | xx | xxxx | |
| Cappuccino is a regular thing. | xx | xxxx | ||
| I don't want to invest more than €500/CHF 600. | xxxx | |||
| I don't want to invest more than €1000/CHF 1200. | xxxx | |||
| The machine should also make coffee at the summer festival at school. | x | xxxx |
Related to the topic:
- Cleaning your espresso machine
- My grind setting is not your grind setting
