Boiler Versus Thermal Blocks

Different Types of Boilers

Inside coffee machines you will find one of three different types of boilers: a single boiler, heat exchange boiler or twin boilers. The boiler is an important focus because it can affect the consistency of your espresso shot-to-shot, as well as being a determining factor in the machines heat up phase and recovery time.

Single Boilers

Single boilers are great for espresso drinkers, as they don’t need to steam milk. They only require one boiler to heat at one temperature. This is a great option for espresso drinkers: they can achieve an excellent result with a smaller price range, without sacrificing temperature stability.

There are multi-function single boiler options, which have the capability to heat up to a level that can produce steam and espresso temperature level water. This is generally controlled by a switch or series of switches.

single boiler diagram, coffee machines

Heat Exchanger

The heat exchanger is located in the main section of the boiler and has a separate tube heat exchanger that runs through the middle of the main boiler. The water in the heat exchange tube is heated by the water from the main boiler and is used for the espresso. The water used for the espresso is generally a combination of hot and cold water to reach the correct temperature. The water in the main boiler runs much hotter than needed for espresso and is used to generate the steam.

Heat Exchanger Boiler, Coffee Machines

Twin Boilers

As the name would suggest, a twin boiler has two boilers: one to create the steam and one to generate the hot water for espresso. Depending on the model of the machine, the water for general hot water (i.e. water used for tea or long blacks) can be generated from either of those boilers


Twin Boilers, Coffee Machines

This is the basic functionality of different boiler configurations, which can be made with different metals as well, including copper or stainless steel. This information is important to know, as some manufacturers or retailers will try to mislead you. For example, they might say they have boilers in their coffee machines, when they actually have thermal blocks. In saying that, it’s also important to know how these machines work and feel secure knowing you’re getting value for money. So what’s the difference? And why does it matter if you have thermal blocks instead of boilers?

Thermal Blocks

Thermal blocks, also known as thermo blocks, are essentially a block of metal with a small passage or torrent that allows water to pass through. This block is heated using an embedded heating element, which heats the block to a suitable coffee temperature as the water is passing through. The water should have reached the desired temperature by the time it exits the thermal block. If steam is required, it will heat to the desired temperature to turn the water to vapour. Thermo blocks are generally found in automatic coffee machines and small department store brands.

Thermal Block, Thermo Block, Coffee Machine

Thermo blocks come in a wide variety of shapes, sizes and quality, and the steam/water output that they can supply varies greatly. The type of material that they’re manufactured from can vary the amount of output, the longevity of the unit and the likelihood of it developing scale blockages. For example, brass thermal blocks are less likely to develop scale than aluminium blocks, but they don’t have anywhere near the same level of heat retention. Therefore the aluminium blocks have much better output for steam and brass is better suited for just coffee.

Thermal Block, Thermo Block, Coffee Machine

Benefits of thermo blocks (dependant on the quality of the actual thermal block, as well as its suitability for the application and equipment choice) include:

  • -Quality consistent dry steam
  • -Consistent water temperature
  • -Energy Saving
  • -Fast heat up
  • -Can be cheaper due to their inexpensive and compact nature

Negatives of thermo blocks (dependant on the quality of the actual thermal block, as well as its suitability for the application and equipment choice) include:

  • -Due to narrow paths, these can quickly get blocked with scale or other foreign matter
  • -Some models can cool off and lose quality when producing large quantities of milk or multiple cups. This can produce wet steam, which is undesirable, and it will then need time to recover. (This is not all that different to traditional boiler machines if you take a lot of hot water from them, as the introduction of cold water to refill diminishes the heat and therefore the steam and water temperature). But considering that the idea of a thermo block is to provide instant consistent steam. It is important to note that it has limits.
  • -Potential shorter life span than traditional boilers. Boilers are theoretically designed to last an indefinite period of time with minimal maintenance, while thermal blocks are renowned for failing within 3-5 years.


coffee machine

If you are looking to buy a coffee machine for home, go to and check out our full range of home espresso machines. You can also talk check out “6 Questions To Ask When Buying A Home Coffee Machine”. If you still have questions or would like to schedule a demo, please contact our office.