How do Espresso Machines Work?

Espresso machines are used everywhere today. You will find them in millions of homes and coffee stores around the world. If you’ve ever used an espresso machine before, you must have wondered how it works. Well, look no further as we explain everything about the inner workings of an espresso machine. Let’s get into it!

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How is an Espresso Shot Made?

An espresso shot is obtained by forcing hot water through finely grounded coffee beans with at least 9-10 bars of pressure. The pressure is generated by the pump while the water is heated in the boiler by a heating element.

What Are the Different Parts of Espresso Machine?

While a good espresso relies on the pressure of the water to brew the coffee, the temperature, filter, and quality of coffee grounds, all affect the final taste and quality of an espresso shot.

To better understand how all these factors affect an espresso machine, we need to look into the different parts of an espresso machine as well as their functions.

There are four main parts of an espresso machine.

  • Water reservoir
  • Pump
  • Boiler
  • Group head

Water Reservoir

The journey of making espresso starts from the water source, the common household espresso machine has a small water reservoir inside it. Professionals use espresso machines draw water directly from the plumbed main connection for use. A good quality espresso needs filtered water with just the right amount of mineral content.


Household espresso machines come with inbuilt pumps because household plumbing does not provide enough pressure for an espresso brew. To extract the flavor from the coffee ground, you need at least 9 bars of pressure.

There are two kinds of pumps used in an espresso machine. For commercial use, a rotary pump is used to get a constant supply of pressure. Whereas for domestic use, a vibration pump is used. The vibration pump is a metal coil around a magnet attached to a piston.

When electric current moves through the coil, it causes the magnet to move the piston rapidly back and forth, this creates pressure when you pull a shot.


The pump pushes the water from the reservoir into the boiler for heating. There are two kinds of boiler systems among espresso machines. A double boiler system and a single boiler system.

A double boiler system is used in high-end machines that allow them to brew espresso and steam milk side by side. Entry level espresso machine to mid-range machines for household often have a single boiler located right above the group head.  

The heat exchanger in the boiler initially brings the water temperature down to 150F. After that, the water for brewing is heated rapidly to 200F whereas it needs 212F for steam. Because of this temperature difference, a single boiler espresso machine can’t brew and produce steam at the same time.

An espresso machine uses either a proportional integral derivative controller (PID) or digital temperature control. These devices help allow you to control the temperature of the water and puts you in control of the brew quality.

Group Head and Portafilter

The true magic happens in the group head located in front of the machine. The group head is where hot water meets the grounded coffee at 9 bars of pressure and the espresso shot is extracted.

There are different kinds of group heads in the market but nearly all of them have the same basic elements. The group head has a portafilter, a tool with a handle, and has basket holding grounded coffee. The group head also has a pressure switch, and portafilter lock to secure the puck while in operation.

The coffee grounds are tamped in the portafilter creating a puck. The portafilter helps create a dense and uniform surface that offers resistance to pressurized water, resulting in an espresso brew.

A dual spout portafilter can help you brew two cups of espresso side by side. The portafilter with a double spout is also called a ‘mustache spout’. The other kind of portafilter is called bottomless (without spout) portafilter.

Kinds of Group Heads

There are two main kinds of group heads, saturated group heads, and unsaturated group heads.

A saturated group head is like an extension of the boiler. This brings the group head to the same temperature as the brewing water. Because of this, saturated group heads are better for maintaining the required temperature.

With semi-saturated group heads, the group head is separated from the main boiler by a heat exchanger. Semi-Saturated group heads struggle with stability when maintaining the right temperature but they are very affordable and easier to repair.

Final Thoughts

Every part of the espresso machine helps make the espresso shot. While operating the machine itself seems easy, the engineering effort that goes into a premium quality espresso machine is a thing to behold. Next time you’re enjoying an espresso, take some time to appreciate the genius of the machine that made it!


What features should I look for while buying an espresso machine?

Before investing in an espresso machine, look into its pump pressure, boiler system, and group head type. Depending on your needs, a double boiler and saturated group head espresso might be good for you. Frothing capability, ease of cleaning, and ease of storage are also some of the features to look for.

Why get an espresso machine rather than a coffee machine?

Espresso machines give a richer and more authentic extraction of coffee flavor. Depending upon your mood and taste, you can make a wide variety of coffee. A regular coffee machine usually does not give you much room for experimentation and improvement like an automatic espresso machine.

What is the difference between an espresso machine and a coffee machine?

A coffee machine makes coffee by using gravity to extract the brew from the coffee ground. Espresso machines, on the other hand, use a pressurized jet of hot water to brew the coffee from the grounds.

Can you use regular coffee in an espresso machine?

Yes, you can use regular coffee beans to make espresso but it will be sour in taste and the extraction quality might not be up to par. Roasted dark coffee beans are better for an espresso shot.

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Evelyn J Stafford

Evelyn is a Coffee enthusiast and writer for Wins Coffee Bar. Her work has appeared in Bean Scene, The Home Kitchen and other publications.

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