How coffee makers work

A close-up of the portafilter on espresso machine as coffee drips from it into a cup
(Image credit: Shutterstock)

Anyone who has one of the best coffee makers will know what a delicious cup of java tastes like, but knowing how coffee makers work is another thing altogether. There are so many different machines on the market and each operates slightly differently, but here we’re finding out exactly how each coffee maker works and what you can use each one for. 

Whether you have an espresso machine, a single-serve coffee maker or a bean-to-cup coffee machine, all coffee makers operate in different ways and each one has different capabilities. Espresso machines are designed to create concentrated shots of coffee but some of these machines have steam wands so that you can create milk-based coffees such as a latte or a cappuccino.  

Pod coffee machines (another name for single-serve coffee makers) are simpler to use but can still create a variety of drinks depending on which pods you buy. Bean-to-cup machines are easier still because they take care of every step in the coffee-making process by grinding the beans, frothing milk, and creating a fully-prepared coffee. There are lots of different types of coffee makers and here’s how each works. 

How do single-serve coffee machines work?  

Single-serve coffee machines, which are often referred to as pod coffee makers, can only dispense one coffee at a time so they’re not ideal if you want to make lots of coffee for lots of people at the same time. Pod machines use capsules that are packed with concentrated coffee ground. Coffee pods are the name given to K-Cups, Nespresso pods, and those flat discs of coffee that slide straight into the machine. 

Pod coffee machines normally have a water tank at the back which needs filling up before you can get started. For the best results, filtered water is recommended especially if you live in an area with hard water. 

The coffee machine then takes the water from the tank so that a heating element can warm up the water. From here, the piping hot water will pass through the coffee pod you’ve placed inside the machine (normally after it has pierced a small hole at the top of the capsule), and concentrated coffee will then drip into the cup you’ve placed below it. 

However, rather than chucking the used coffee capsule in the garbage - it's estimated some 56 billion single-serve pods end up in landfill each year, find out how to recycle Nespresso Pods, along with other brands of coffee capsules, to make using this type of coffee machine more sustainable. 

How do espresso machines work?  

In the same way that pod machines have a water reservoir, espresso machines also need water in order to work. Professional espresso machines are normally plumbed into a mains water supply, but for home use, espresso machines have a water tank. The same idea of using filtered water also applies to every type of coffee machine, and this isn’t only because it affects the taste, but because it helps to minimize calcium build-up in the machine’s pipework. 

Espresso machines create strong, concentrated shots of coffee but in order to get the water from the reservoir and through the ground coffee, they require a powerful pump. The power of these pumps is measured in bars and the industry standard for an espresso machine pump is nine bars, although you can get models with an even higher bar.

Having the power to push water through the ground coffee is all well and good but this won’t heat the water up and that’s where a boiler comes in. Some espresso machines have just one boiler that heats up the water and others have two boilers so that water and milk can be heated simultaneously. You can also buy fancier machines that heat the water and then store it so that it’s ready for when you want to make another drink. 

Different espresso machines will offer different levels of control over the temperature of your water. More affordable machines sometimes don’t even offer the option to adjust the water temperature, whereas, more expensive models have digital controls that allow you to adjust the temperature.

For espresso machines with dual boilers, the water is heated to different temperatures. One boiler will heat water so that it’s just the right temperature for pushing through the ground coffee to make a good shot of espresso, the other boiler will heat the water so that it’s hot enough to create steam ready to travel down the steam wand to froth milk.

Once the boilers have heated the water to the optimum temperature, the water then drips through the group head and through the portafilter, which is the basket that holds the coffee and sits in a handle that you twist into place.

You can find out in-depth how to use an espresso machine in our article. 

An espresso in a glass cup being held by two hands

(Image credit: Getty)

How do bean-to-cup coffee machines work?

Just like the espresso machines, bean-to-cup coffee makers, which are sometime also known as automatic coffee machines, push pressurized hot water through a disc of ground coffee to create a short, intense espresso. However, this whole process is handled by the machine; from grinding the beans and compressing the grounds into a puck, to dispensing the correct volume of water - meaning you can get a consistent coffee every time with just one or two taps. 

There are two styles of bean-to-cup coffee machines on the market - those that have a manual steam wand and those that come with the ability to dispense perfectly texturized milk into the coffee to create barista-style drinks with minimal input from you. 

The hands-off machines that take care of milk texturizing along with everything else typically offer a selection of coffee types on a menu screen. You can choose between coffee shop favorites such as intense espresso, frothy cappuccino, silky latte, or flat white. Then fill the built-in carafe with milk, so the machine can texturize it and dispense the correct amount for the coffee selected. Often the milk carafe is removable so you can pop it back in the fridge between coffees and avoid the horror of sour milk in your drink.

Alternatively, those that come with a manual steam wand, let you select a coffee base for your hot drink; for example, a single or double espresso or a longer coffee such as a ristretto and it dispenses it into a cup. It's then up to you to fill a jug with the correct amount of milk, or a non-dairy alternative, for your desired coffee-based drink and texturize it before adding it to the cup. 

Discover in more detail how bean-to-cup coffee machines work in our article. 

How do filter coffee machines work? 

Filter coffee machines are sometimes called drip coffee makers and these machines feature a basket where you place a filter and the ground coffee, a water reservoir, and a carafe where the brewed coffee drips into. As with all other machines, the coffee maker will require water to get to work. 

The water will be warmed up by a heating element coil and that hot water is then passed into the filter basket via tube. The hot water is dripped through on top of the coffee grounds and this then passes through a filter to end up in the carafe below. The heating element also heats a hot plate beneath the carafe so that you can keep the coffee warm after it has brewed.

How do French press coffee makers work?

French press coffee makers are manual machines so they’re pretty simple to understand. After placing ground coffee in the carafe and adding hot water, the plunger on a French press coffee maker has a circular filter that stretches the entire diameter of the carafe - after a few minutes, this filter is pushed down and separates the coffee grounds from the brewed coffee.  

Sophie Bird

Sophie writes about all things appliance-related and is currently the Home Editor at TechRadar's sister site, Top Ten Reviews. When she's not testing coffee machines and appliances, Sophie is thinking of eating delicious food, and asking people what they're having for dinner.

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