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How Do Home Coffee Machines Work?

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Table of Contents

An Introduction To Coffee Machines In The Home

Sipping a delicious cup of freshly brewed coffee in the morning has become a daily ritual for most Australians. As a result, the need to have a coffee machine in your home has become more vital than ever. The ability to make a fresh cup of coffee whenever you want has become a prerequisite to modern life. However, for some, the question still remains, how exactly do these home coffee machines work?

Coffee machines can come in a wide variety of different shapes and sizes depending on the brand and model you buy. It’s important to note that whilst most coffee machines follow the same fundamental process. Firstly, water is heated in a temperature-controlled boiler, where it is heated to an optimal coffee brewing temperature of 90-96°C. Next, the water is sent through the finely ground coffee at an ideal pressure to produce excellent delicious espresso. Some machines will also have steam wands that can texture milk for your cappuccinos and lattes, but more later.

Firstly, it’s important to understand that there are many different types of home coffee machines. They range from manual espresso machines, such as the Rocket Espresso R Nine One, all the way to automatic Delonghi Maestosa.

Although there are many types of home coffee machines, this blog will cover manual home coffee machines and home automatic coffee machines.


Manual Home Coffee Machines

These manual home coffee machines are often also known as home espresso machines. They’re known for brewing high-quality shots of espresso in small quantities. 


Main Components

1. Water source/feed

A reliable water source is imperative for home coffee machines. Generally, water will end a coffee machine in two different ways. Either the machine has a water reservoir located within it somewhere (to contain the water), or there is an established connection to plumbing whereby a sustainable flow of water can enter the machine.

A water reservoir typically is the best option when used domestically, in a small household, producing relatively small quantities of coffee. With this water source, you can easily control your water quality rather than being at the whim of a tap. When filling your machine, you’ll want to ensure you’re using filtered water poured from a clean container.

Let’s use one of our personal favourite home coffee machines here at Coffee Complex, The Rocket Espresso Appartamento. With this coffee machine, you can choose either hard plumbing or a water reservoir.

2. Boilers

The coffee machine’s boiler(s) is/are responsible for storing, pressurising and adding heat to the water from the pump. The more coffee you’re looking to make, the greater the boiler size you’ll need. However, it’s important to remember that the greater the boiler’s size, the longer you’ll need to wait for the water within to heat up. For reference, the Rocket Espresso Appartamento Coffee Machine has a 1.8-litre heat exchange boiler. 

Some more advanced coffee machines have PID devices, which allow you to keep exact control over your coffee machine’s brewing temperature. A PID is a simple computer that you can use to control the heating element and keep the water at the desired temperature. However, remember that this only comes stock standard with some home coffee machines on the market.

Coffee machines with a single boiler are generally better if you make fewer cups of coffee and have fewer time constraints. You’re limited to one heating element with a single boiler, meaning you cannot pull a shot of espresso and steam milk simultaneously. However, this issue can be solved if you utilise a heat exchanger. Depending on how busy you are and how many coffees you need, you’ll know whether a single or dual-boiler coffee machine is right for your home.

If you’re making lots of coffee, time is of the essence. Then a dual boiler is a way to go, as you can brew coffee and steam milk simultaneously. As aforementioned, the temperature for boiling water and creating steam is vastly different to that of the temperature required for brewing coffee. This boiler configuration moves water to each boiler separately. One boiler is responsible for heating the water to a boiling point, and the other for the perfect coffee brewing temperature. It’s important to remember the difference between the temperature required to boil water and the temperature required to brew coffee, which is 90 – 96 degrees celsius. Generally, machines with dual boilers can cost more money, but with that, you gain a greater amount of reliability and control over your delicious brew.

3. Steam wand

If you’re looking to drink lattes and cappuccinos, you’ll want to know how to operate a steam wand on your coffee machine at home. To steam milk for your coffee, your machine needs to create steam from the boiled water. The steam wand is used to heat your milk and produce froth, perfect for a delicious cappuccino.

4. Group head

There are only a few primary styles of group heads. The Rocket Espresso Appartamento Coffee Machine uses an E61 group head and thermosyphonic system to deliver optimal flavours for espresso. The group head can take 15 minutes to get to the ideal temperature. The shot pouring is not automated, meaning you get the opportunity to take full control over the length of time the shot pours and, thus, the shot’s volume.

The E61 group head consists of three valves, each with a unique purpose. One valve facilitates water movement from the boiler into the group head. Another is responsible for moving water from the group head into the portafilter, and finally, the third valve is used to alleviate back pressure from the portafilter.

5. Portafilter 

The portafilter is simply a portable filter for your home coffee machine. Within it resides a metal filter basket. Although simple, the portafilter is still a crucial component of the functionality of a manual home coffee machine. You’ll put your ground coffee beans into here before pressing with a tamp. After you’ve tamped your coffee beans, you’ll lock your portafilter into place and insert it into your coffee machine.

Portafilters can come in all ranges of sizes. So if you’re buying an extra portafilter for your coffee machine, be sure to match it to the size of your tamp. Otherwise, you might need help to tamp your ground coffee beans properly.

Coffee Making Process

Extracting The Perfect Espresso On A Home Coffee Machine

  1. The amount of flavour you extract from your beans is determined by the extraction rate.
  2. The aim is to extract 50-60 ml of coffee from the double handle in 25-30 seconds.
  3. The grind settings control the rate at which the water flows through the coffee
  4. An espresso grind is very fine but still granular. The finer the grind, the slower the coffee grind. The coarser the grind, the faster the coffee will extract.
  5. It’s best to use a burr grinder, that will allow you to adjust the grind setting.
  6. Overfill the handle with fresh grounds and sweep the excess grounds back into the doser chamber to create a level surface flush with the basket’s rim. 
  7. Compress the grounds firmly using a tamper. 
  8. The compressed grounds should reach the reference line in the basket.
  9. Insert the handle into the group head and lift the lever to start the extraction. (Not all home coffee machines will have a lever)
  10. It should take 25-30 seconds to get a double shot of espresso.
  11. Extraction should begin with a few seconds delay while the water is saturating the grounds.
  12. Then, droplets will turn into a slow, even pour. 
  13. Stop the extraction at 50ml or when the pour lightens.
  14. Espresso should be thick, rich and flavourful with a dark foam or crema on top.


Operating The Steam Wand To Texture The Perfect Jug Of Milk

  1. Start with a 600ml jug that’s half full of fresh cold milk—the fresher and cooler the milk, the better the result. There are three primary steps to steaming thick, velvety smooth milk.


  2. A thick texture is produced by folding the air into the milk. Ensure the steam nozzle is only just under the surface of the milk. If the steam nozzle is too deep, the milk will end up thin, and a screeching sound will accompany the steaming. The correct technique will produce a sipping sound and the presence of very fine bubbles.


  3. To ensure the bubbles fold into the milk, position the wand to the side and create a whirlpool. The optimum temperature for milk is 70 degrees Celsius, which is generally achieved when the side of the jug is too hot to touch.

You’re well on your way to becoming a pro home barista. If you’re still yet to purchase a coffee machine for your home, you might be wondering, are home home coffee machines worth? Check out our blog to learn more.

Automatic Home Coffee Machines

There are wide varieties of automatic coffee machines you can choose to use at home. These range from semi-automatic, fully automatic and super-automatic. As the name suggests, the greater the autonomy, the fewer stamps involved in brewing that delicious coffee. These automatic coffee machines take some guesswork out of brewing coffee at home. If you need to become more experienced with coffee machines in the home, then this might be the best option for you. Let’s dig a little deeper and examine how these machines work.

There are different levels of automation available in home coffee machines. Many models can grind beans, and some can froth milk and self-clean. Automatic coffee machines with integrated grinders can produce a range of flavours and grind the ideal amount of beans for each cup, ensuring that the coffee stays fresh. These machines often offer a variety of drink settings, allowing users to create professional-quality coffee drinks without needing expertise in coffee-making techniques.

Home Automatic Coffee Machines vs Manual Home Coffee Machines

Automatic coffee machines operate using processes similar to manual coffee machines but offer the convenience of producing a cup of coffee with the press of a button, from grinding the beans to pouring the final product. If you’re curious about how to pick a machine for your home, read our blog about how to choose a home coffee machine.



If you are looking to buy home coffee machines in Australia, you can purchase from our fantastic range online! If you live in Adelaide, swing past our store in Adelaide, Australia and purchase in-store. We’re located at 18 Croydon Rd, Keswick SA 5035.

Got questions about our range of home coffee machines?

Give us a call at (08) 8297 5799 or email us at


Resources & Reference List

How To Make Great Espresso by Rocket Espresso

Rocket Appartamento from Rocket Espresso

About The Author

Picture of Anthony Maione
Anthony Maione

Anthony is a coffee machine sales and repairs specialist living in Adelaide, South Australia. He has spent the last 14 years staying at the forefront of the coffee machine industry. He has sold hundreds of home and office coffee machines throughout all of South Australia and has also repaired countless machines.

Occupation: General Manager, Coffee Complex
Lives in: Adelaide, South Australia

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