How Does an Espresso Machine Work? A Complete Guide

Getting into making espresso at home is a significant step in the world of coffee, not only because espresso flavor is more nuanced, but also because the equipment is far more complex than a standard drip machine or manual method of brewing. One of the first steps to making high-quality espresso at home is learning how an espresso machine works. That’s exactly what I’ll go over in this guide.

As someone who’s been obsessed with espresso for years (and has spent way too much money on equipment), I can say that understanding how these machines work is an important part of making delicious espresso at home. If you’re thinking about buying an espresso machine, the last thing you want to do is drop $1,000 or more, get it home, and realize that you can’t make good coffee until you learn how to use it. So…let’s learn!

What Are the Parts of an Espresso Machine?

Before we dive into how an espresso machine works, you need to have a basic understanding of the components of an espresso machine so that you’re not instantly lost. Here’s a rundown of every single part, what it does, and how it functions:

Portafilter: This is the handle that holds the filter basket packed with ground coffee. It’s removable so you can easily discard the spent puck after each shot.
Filter Basket: A small basket that fits into the portafilter and holds the ground coffee. Different sizes allow for varying dose weights.
Tamper: Not technically part of the machine, but you usually get one with your espresso maker. You use this to pack down the coffee inside the filter basket.
Group Head: The part of the machine where you lock in the portafilter. Water is forced through the group head, into the filter basket, and through the packed coffee puck.
Brewing Boiler: A small boiler that heats water to the optimal brewing temperature (just below boiling) for espresso extraction.
Steam Boiler (only on machines with double boilers): A separate boiler that heats water to produce steam for steaming milk. Having a dedicated steam boiler allows for better temperature stability in the brew boiler.
Pump: Generates the 9 to 15 bars of pressure required to force water through the packed coffee puck.
3-Way Solenoid Valve: After brewing, this releases the remaining pressure from the group head to allow removing the portafilter.
Steam Wand: A metal wand connected to the steam boiler that aerosolizes steam for heating and frothing milk.
Drip Tray: Catches stray espresso, water, and steam from the brewing process.

Got all that? Good. Now we can dive into how an espresso machine works to transform water and ground coffee into delicious espresso.

How Does an Espresso Machine Work?

An espresso machine is essentially a unique way to control precise temperature, pressure, and shot time during the brewing process. Here’s a basic overview of how it all works:

The water reservoir feeds into a small brew boiler and gets heated to the optimal brewing temperature, around 195 to 205 degrees (F). Some machines use a water pump to move the water into the boiling chamber, but others rely on gravity.
When you activate the brew cycle, a water pump forces hot water through the group head and into the portafilter basket packed with finely-ground coffee. The compacted coffee and the tiny perforations in the bottom of the filter basket help create a seal that produces pressure and prevents the water from shooting out immediately into your espresso mug.
The hot water slowly passes through the tightly-packed coffee puck, extracting those delicious coffee compounds.
The concentrated coffee liquid, now espresso, flows from the basket into your cup in about 25 to 30 seconds for a typical shot.
If your machine has a milk steamer, then it will begin heating water for steaming at this point. Entry-level machines only have a single boiler, so you’ll have to wait for the water to reach the proper temperature before steaming. Higher-end machines have dual boilers that provide instant steam, and some use heat exchangers that still need to heat up but reach temperatures more quickly than single-boiler machines.

Now let’s examine each of those steps in more detail to get a better understanding of the process from start to finish.

Temperature Control

Consistent temperature is vital for quality espresso. Too cold, and you’ll under-extract, resulting in sour, underdeveloped flavors. Too hot, and you’ll burn and over-extract, leading to harsh, bitter notes in your cup.

Most home machines use a thermoblock or thermocoil to heat water from the reservoir to reach the proper brewing temperature. These transfer heat relatively well but can fluctuate during the brew cycle.

More advanced models use a brew boiler, which is an enclosed tank of water heated from below to precise brewing temps. Some of the higher-end machines include a PID controller, which dials in precise temperatures and holds them effectively. As water exits the brew boiler, it’s replenished from the reservoir and the heating element heats up to keep the temperature stable.

Prosumer dual boiler units go a step further, adding a dedicated steam boiler so steam production doesn’t affect brewing temperature, or the other way around. You’ll notice quickly how much easier temperature stability is on a well-designed dual boiler, especially if you’re brewing espresso followed immediately by steaming milk for a mixed coffee drink.

Many manual lever espresso machines (more on these later) rely on an external heating source to heat up your water and hit the temperatures required for proper extraction. For example, with the Flair Pro 2 (one of my favorite manual espresso makers), there’s no heating element at all. Instead, you boil water, add it to the brewing chamber, and then press down on the lever.

Pressure Control

Pressures of around 9 to 15 bars are required to extract espresso properly. Too little pressure, and your water will slowly drip through the puck of coffee, leading to long extraction times and bitter, burnt flavors. Too much pressure, you’ll either push the water through the puck too quickly, leading to underextraction and sour flavors, or the puck will compress under the pressure and not let any water through. This is called a “stuck brew.”

The pump is responsible for generating the right amount of pressure. Cheaper models use vibratory pumps which, in my experience, can be inconsistent. More expensive machines opt for rotary or gear pumps that maintain very stable pressure throughout the entire shot. Manual level machines rely on your muscle to create the pressure using a lever.

Some higher-end electric units even let you adjust pump pressure up or down to fine tune extraction, similar to what you could do with a manual espresso maker. This is called “pressure profiling.” This level of control really lets you dial in your shot for different coffees.

Consistent pressure combines with stable temperature to enable the extremely small window for proper espresso extraction.

The Portafilter

This component seems simple, but the portafilter is an essential component. It locks into the group head, creating a sealed chamber where the pressure magic happens.

You’ll need to master portafilter preparation, including leveling and tamping the ground coffee into an evenly distributed, tightly-packed puck to get proper espresso flavor. Too loose, and water will simply run through, leading to underextraction. Too tight, and you’ll choke the machine.

After the shot, engaging the 3-way solenoid valve releases the built-up pressure so you can safely remove the portafilter without making a mess. BE WARNED: some entry level machines don’t have this solenoid, so if you try to unscrew the portafilter before it naturally loses pressure, coffee and water will shoot out all over your kitchen. I’m speaking from experience.

The Group Head

The group head is where the portafilter locks in. It sometimes has a diffuser screen that helps evenly disperse water over the coffee puck.

On the more basic models, the group head is part of the thermoblock heating system, which can cause temperature fluctuations. More advanced machines integrate a brew boiler that maintains precise temperature stability.

The whole magic happens when heated water from the boiler is forced through the group head, into the packed coffee in the portafilter basket, and out into your cup. It’s simple in theory, but infinitely complex in practice.

Types of Espresso Machines and How They Work

There are a few different types of espresso machines, each working a bit differently and requiring varying amounts of effort from you as the barista. I’ll explain how each type of machine works in the following sections.

Manual Lever Espresso Machines

These old-school beasts ditch the pump and often the heating element and have you provide hot water and manually generate the 9 bars of pressure required via a lever-operated piston.

Rather than electric pumps, the pressure mechanism is fully manual. You first load the group head or brewing chamber with grounds, add your hot water, and then use the lever to force down the piston and pull a shot. Some good ones include a pressure gauge to keep track of the force you’re applying. It’s a very hands-on, ritualistic process.

Manual levers put you in full control of all variables: grind, dose, tamp pressure, shot volume, extraction time, and temperature (in many cases). More control means more customization and tinkering, but that also means a steep learning curve to master all those elements.

With no automated anything, consistent shots require intense focus and feel. I love the zen-like routine, but it’s not for the faint of heart. It took me weeks to get used to the process before I was pulling good shots with my Flair Pro 2.

Semi-Automatic Espresso Machines

These autobrew units automate the overall shot process, but still give you control over some key variables.

To brew, you’ll still need to grind your coffee, dose, and distribute and tamp the coffee puck in the portafilter. You also remain in control of the shot time, as there’s a dial or button to control when the pump starts and stops pumping hot water into the brew head. But from there, the machine takes over.

You’ll lock the loaded portafilter into the group head, then activate the pump which sends water from the boiler at the ideal pressure. Just switch the pump off at your desired shot time. The automation ensures consistent parameters for temperature, pressure, and total shot volume if your puck prep and shot time are on point.

However, you can still manually stop the pump whenever you feel the shot is blonding, letting you adjust the yield and overall brew ratio.

Most quality semi-automatics are available in both single boiler or dual boiler (brew plus steam) configurations. I highly recommend dual to maintain stable brew temperatures when steaming milk.

Overall, semi-automatic machines provide a fun balance of tech and hands-on work.

Automatic Espresso Machines

These take most of the effort out of the equation, doing almost everything besides grinding the beans and preparing the puck.

To operate an automatic espresso machine, you’ll simply grind your beans, dose into the portafilter, distribute and level the grounds, and lock the portafilter into the group head.

From there it brews similarly to a semi-automatic machine, although it also controls the shot time. Some machines let you override for manual control if desired.

With all variables calculated and programmed, these are incredibly consistent shot-to-shot once dialed in. But you are limited to the machine’s single dose/yield setting without the ability to adjust grind size, dose, or ratio between shots easily. For some, that lack of control is a deal-breaker. For others, the convenience is well worth the loss of brewing control.

Automatics machines deliver consistently delicious espresso with basically zero effort beyond grinding and tamping. It’s taste with convenience: a perfect for busy home baristas.

Super-Automatic Espresso Machines

Taking automation to the max, these bean-to-cup beasts handle literally every step automatically at the push of a button.

You’ll add whole bean coffee to the built-in grinder hopper, which automatically doses and tamps for each shot. The machine controls all pressures, temperatures, and volumes for seamless, volumetric brewing.

Even better, many super-automatics froth and combine steamed milk into your brew automatically for hands-free drinks like lattes and cappuccinos. All you do is press a button, and it delivers a ready-to-drink beverage.

For sheer convenience, super-autos reign supreme. From a technical and taste perspective though, the lack of any user control means you’ll never be able to fine tune or make adjustments on the fly. I personally don’t like these, but if you don’t care about maintaining control over your coffee, they might be ideal, provided you can stomach the steep price tag.

Using Your New Knowledge of How an Espresso Machine Works

Understanding how an espresso machine works is the crucial first part of learning how to make high-quality espresso at home. Now that you’ve geeked out on the mechanics, I recommend reading my article on the science of espresso brewing so you can understand how all these components and controls affect the actual taste in your cup.

After that, you’ll be armed with all the knowledge needed to decide what kind of espresso maker is right for you. You can weigh convenience against control and make an informed purchase on your first home espresso setup to ensure the best espresso machine possible for your specific needs.

Frequently Asked Questions

What is the most important part of an espresso machine?

While every component plays a crucial role, the most important part of an espresso machine is arguably the brew boiler or thermoblock. Precise temperature control between 195 and 205 degrees (F) is vital for proper espresso extraction. Too hot or cold, and you’ll over or under extract, resulting in harsh bitterness or sour flavors. A high quality boiler that maintains extremely stable brew temps is key for delicious, balanced shots.

Can I use a regular drip coffee maker to make espresso?

No, unfortunately regular drip coffee makers cannot make true espresso. Espresso requires 9 to 15 bars of pressure to extract the concentrated coffee oils, compounds, and flavors properly. Drip machines only produce around 1 to 2 bars of pressure. While you can make a strong, concentrated coffee with a drip maker, it won’t have the same syrupy body and aromatics as espresso brewed under high pressure. You also won’t get that delicate, lightly sweet crema from a drip machine.

How often should I clean my espresso machine?

Espresso machines require diligent cleaning to prevent oil buildup and ensure great tasting shots, so you should plan on a routine espresso machine cleaning daily and a deep cleaning about every 2 weeks. The brew group, portafilter, and baskets should be cleaned after every use by backflushing and removing spent grounds. A deeper cleaning with espresso machine detergent should be done every 2 weeks or so. Following the manufacturer’s descaling recommendations for the boiler is also crucial to prolong the lifespan of the machine and ensure high-quality coffee every morning.

What’s better, a semi-automatic or super-automatic espresso machine?

There’s no definitive “better” choice, as it depends on your priorities. Semi-automatics require more hands-on work like grinding, dosing, and tamping, but allow more control over variables, including dose, shot time, and yield. Super-automatics make the process extremely convenient by handling everything automatically, but they limit the ability to make adjustments. Those wanting maximum control should choose semi-automatic, while those prioritizing convenience may prefer super-automatic.