Espresso Machines Explained: How Do They Work?


Ever since we were little kids, we’ve always wanted to know how things work. We would break our toys apart just to see if we could get a grasp of its functioning.

As adults, this didn’t change a lot. But don’t worry! We’ll help you understand, piece by piece, how one of your favorite machines work: The Espresso Machine.

We want to explain it to you in the most simplistic way. So we’ll review the espresso machine the same way water goes in: First into the water tank – passing through each of the important parts. Eventually making our way out, we’ll finish with water coming out of the grouphead or the steam wand.

Espresso Machines Explained: How Do They Work?

Water Source

There are two ways to provide water for your espresso machines— via a water tank or a “consistent water source“.

The water tank is the most common and convenient source. For home and casual use, water tanks are the norm. Even with big machines, water tanks are still a viable option; with about 5 liters being the biggest we’ve ever seen. Regular machines, however, can hold about one liter in their tank.

The second option, usually referred as “consistent water source”, is typically used only for big machines. In establishments that serve over two or three hundred cups of coffee a day, having a water tank hinders their productivity. Hooking their espresso machine to a consistent water source saves time, effort, and money.

As a sort of third option, there are some machines that combine both features. These machines work by having a sizeable water tank which can be refilled both by a consistent water source or manually.

Water filtration systems

An important part of the water source, be it tank or constant, is implementing a water filter.

Water tanks have a filtration system incorporated, so that filtration occurs either as it is sitting in the water tank, or as it leaves the water tank and goes into the pump.

When a machine is directly hooked to a constant water source, the filtration system is placed between this source and the machine. This way, the water is already clean and pure when it reaches your espresso machine. (With one downside being that these systems are more complicated to install. And more expensive).


The thing that distinguishes espresso from most other types of coffee is its different brewing method. In fact, coffee isn’t “brewed” at all when making an espresso. Hot water is pushed through the coffee grounds at a high pressure, condensing all the brewing time in about 10 to 20 seconds.

As a result, less water is needed, and we achieve a much higher concentration of coffee than we are used to. Plus, of course, a better aroma and flavor.

Thanks to modern technology, we don’t need to actually pull a shot of espresso: This term is born from old espresso machines that needed the barista to operate a lever. This is what created the high-pressure that enables us to extract our beloved espresso.

Vibratory pump

This pump works via pistons, just like diesel engines in a way. The piston is attached to a magnet, and inside is a metal or copper coil. Electrical current is then run through the metal coil: This causes the magnet to make the piston move back and forth rapidly or, to put it simply, vibrate.

This vibration is what makes espresso machines particularly noisy.

Rotary pump

Now, these are a little more complicated. The rotary pump is actually mechanical (as opposed to electrical), which means that it uses electricity in a different way than vibratory pumps.

Rotary, because it spins, of course. It consists of a circle-shaped chamber with a disc inside which will spin. As it spins, it gains force with movement. Water enters the chamber and is then pumped out with the force of the rotating disc.

What’s the difference?

While both of these pumps produce, essentialy, the same quality of coffee, the difference comes down to cost.

Rotary pumps are much more costly, and are chosen for expensive, commercial-type espresso machines because they last longer.

Vibratory pumps, on the other hand, more affordable. But they are not as reliable as rotary pumps, and have a shorter lifespan.

Espresso Machines Explained: How Do They Work?


As you could probably tell by its name, the boiler is in charge of water temperature. Boilers are of a smaller size than water tanks, designed to heat water in order to make no more than a few drinks at a time.

While there are many types of boilers, we will see two major types: The first works much like a thermostat. It will switch on the heat whenever you tell it to and whenever its internal thermometer reaches a certain temperature, it will switch off.

Yet boilers can be much more complex than that. Many different ways to monitor temperature have been implemented in newer, more expensive machines. The reason is that simpler boilers tend to overheat the water, essentially “burning” your coffee more often.

The solution to this problem varies from machine to machine. Some will implement mechanisms that digitally control temperature, which is much more precise than relying on thermometers. There’s also a system that monitors temperature constantly, switching off the heating element moments before the desired temperature is reached; This avoids going over by a degree or two. 


A grouphead consists of several small parts. The outermost one is the part where the hot water comes out. We tend to refer to this part, the one we lock the portafilter onto, as “the grouphead”.

…But this is not 100% correct. The grouphead serves other functions – and different machines will have different types of groupheads. A grouphead can be modified to include, for example, a pre-infusion function on your machine.

The most common type of grouphead serves as a separate entity from the boiler. As soon as the water from the boiler is heating up, the innermost part of the grouphead will start heating, too. It’s important to preserve temperature, so the grouphead must not be cool or warm; It should be hot.

Once the grouphead achieves the right temperature, it sends a signal to the boiler and now your machine can start a shot.

There’s one notably different type of grouphead: The “saturated” grouphead.

It gets its name because the innermost part of this type of grouphead is connected to the boiler and will become saturated with hot water right from the boiler. While this type of grouphead is much more efficient at reaching the optimal temperature for pulling a shot, it’s much more expensive.

Espresso Machines Explained: How Do They Work?


This is the emblematic part of the espresso machine. Whenever you think of a barista, you see them with a portafilter in their hand.

Technically, however, the portafilter is a part of the grouphead. It is only complete when the portafilter is attached.

Portafilters are very standard across most espresso machines. They don’t really vary in size more than a few millimeters, and the most significant differences you’ll find are on the handle. The handle is oftentimes covered with an outer layer of heat-resistant material so your hands don’t get burnt.

Besides that, all portafilter consists of two simple things: a handle, and a basket.

The basket is where you put the coffee grounds and the handle is, well, you know… A handle.

Steam Wand 

Nowadays, you can’t really talk about coffee without talking about milk-based drinks.

Lattes, in particular, have risen to the top of the coffee chain and might just be the most popular coffee drink. When you take into account that coffee itself is the world’s most popular beverage, it sounds even more impressive.

But not every espresso machine has a steam wand. Why, do you ask, would anybody sell an espresso machine that doesn’t have a steam wand?

It all comes down to water temperatures. As we explained earlier, water is heated in the boiler. We also said that it is very important for this water not to exceed certain temperatures and all these features for controlling water temperature.

To extract a coffee, the ideal temperature is between 85 and 95 degrees celsius. Anything above that will lower the quality of the coffee. But to create steam you need actual boiling water. So it becomes impossible to have both features at the same time.

One way to compensate for this is to put an additional boiler into our machine. This boiler will, then, be used exclusively for creating steam.

But of course, not many machines can afford this. It requires more space -making the machine chunkier- and, more importantly, more money. So many manufacturers opt out of the steam wand feature, and some offer less-than-ideal substitutes.

And that, ladies and gentlemen, how espresso machines work.

Now, who wants some coffee?

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