May 28, 2022

Espresso Machine Boilers: Which One Should You Choose

When buying an espresso machine, it is important to know what kind of boiler it has. The type of boiler will dictate how your machine brews your coffee and the setting that you are working in. Which is why we couldn't agree more with the statement that "the boiler is the heart of the espresso machine".

Cross-section of a double boiler machine.

Each type of boiler has different uses, and its own pros and cons. You wouldn't want to choose a machine that has boiler intended for home use when running a café, and vice versa.

So, in this blog, we'll run through the different types of boilers, the price point, and why the type of boiler matters when choosing an espresso machine.

There are three main types of boilers:

Thermoblock
Single Boiler
Heat Exchanger
Dual Boiler

Thermoblock

A thermoblock is a heating element used by some coffee machines (widely used in capsule coffee machines and the like) to heat up the water used to brew coffee in the shortest possible time.

Unlike a boiler, a thermoblock does not store water but rather takes it directly from the tank, passes it through a maze-like set of pipes (the thermoblock), and heats up the water before exiting to the group head. By the time it reaches the group head, the water temperature is hot enough to brew coffee or steam milk. This process usually takes less than 30 seconds, which makes thermoblocks very efficient and popular.

Water is heated as it goes through the "maze" in a thermoblock.

Why would one consider a thermoblock espresso machine? It warms up faster than a traditional boiler and cost much less to produce. You can get your coffee within minutes after turning it on, as compared to a boiler espresso machine that needs a longer period to warm up.

However, due to its design, thermoblock do not have good temperature stability. The fluctuation of temperature can cause bitterness when there's too much heat and sourness when heat is too low. It is also susceptible to limescale build up, which can affect the water flow.

While a thermoblock is not a boiler, understanding how it works can help you make a more informed decision when purchasing an espresso machine.

Single Boiler

Are you transitioning from café to home espresso? If so, a single boiler is a great place to start!

As the name implies, it only has one boiler to brew espresso and steam milk. Single boilers are generally smaller and less expensive than other types of machines, which means they're easier to store and more portable.

Although, a single boiler machines can't brew and steam at the same time—you'll have to wait for the boiler to get up to steam temperature after brewing (which could take up to a couple of minutes). You'll also have to wait for the boiler to cool down before pulling another espresso.

That said, if you're just pulling an espresso or a long black, it won't matter much. But if you're planning on making a latte or having guests over and need your machine up and running all day long, it can be time-consuming to work with a single boiler machine.

Heat Exchanger

A heat exchange boiler falls somewhere in between single and dual boiler.

It is a single boiler machine that can brew and steam at the same time, all thanks to the heat exchanger! It has a big steam boiler that produces a ton of steam power to get your coffee going.

In order to produce brew water (which is around 94 degrees Celsius), a tube goes through the center of the steam boiler and then goes to the group head.

When you are pulling an espresso, the pump draws water from the reservoir, and the hot water in the steam boiler heats the water as it goes through the tube without bringing it to a boil.

Any leftover water in this tube after the shot will most likely need to be flushed as it will keep getting hotter because of the temperature of the steam water.

A simple diagram on how a heat exchanger works.

The benefit of a heat exchanger is that you get loads of steam power for the price and you can pull many consistent shots compared to a single boiler.

However, because of how this process is designed, it means that you don't have direct control over the water temperature that's being used for brewing. A heat exchanger is still only using one boiler, so it can only pull so many shots before requiring warm up time.

Dual Boiler

If you are looking for a boiler that can brew and steam at the same time, and also withstand high volume, a dual boiler is the perfect choice. A dual boiler machine uses two boilers (steam boiler and brew boiler), each with its own heating element. This allows for the boilers to be ready at all times. Similar to heat exchange, brewing and steaming can take place at the same time, but what are the difference?

Well, there are a few. A major one would be the brew temperature. To keep the temperature consistent, a dual boiler machine is usually equipped with a PID controller, which keeps the temperature of the boiler consistent. Having a separate boiler for brewing also helps to maintain thermal stability, which will result in consistent shots and also allow you to pull back-to-back shots much longer and better than a heat exchanger.

So, what's the drawback with dual boiler? Firstly, as you might have guessed, is cost. Dual boilers pack much more material and obviously, due to that reason, it takes up more space. It also packed with a lot of commercial features that requires a bit of training to get used to.

There are also espresso machines that are considered "multi-boilers", essentially a machine with more than two boilers (dual and multi boiler terms are used interchangeably). For example, a machine with two group heads could have up to three boilers; a steam boiler and two brew boilers for the two group heads. Depending on the machine, you can individually adjust the temperature for each group head.

So, Which One Should I Choose?

This may seem like a difficult question, but it really boils down to what you're going to use your espresso machine for.

If you are a home user who only drinks about a cup or two daily, then the single boiler is the right choice. Single boiler machines are relatively less expensive. They are also smaller in size than other types of machines, so storing it in your home should not be a problem. Maintenance cost is also cheaper as it packs less material.

On the other hand, if you drink more coffee than an average person would, you should opt for the heat exchanger as it can pull more shots than a single boiler. Apart from being able to brew and steam at the same time, a heat exchanger is also ideal for those who love to host guests over, or if you own a small business.

Lastly, if you own a café that requires shots to be pulled back-to-back, you're gonna need a dual boiler. A dual boiler can keep up with the demand of a busy café, especially when it comes to high volume scenarios. It is also usually packed with all the "must have" features such as multiple group heads, PID controllers, steam check valves, saturated group heads, and other high-end features. All of these features allow you to not only pull back-to-back shots, but also brew a ton of milk coffees without a hiccup.

Now that you're equipped with the right knowledge on how these boilers differ from one another one, you can visit our website for an array of espresso machines! You can contact us if you are still indecisive. Our team of experts can help you to decide on which machine suits best according to your needs.