Dual boiler coffee machines. Why?

Should you spend your money on a coffee machine with two boilers?

Before we draw any conclusions about this, let’s look at the reasoning and thinking behind a coffee machine with more than one (usually two) boilers. Here are the key factors to consider:

  • Getting the temperature spot-on. Great tasting coffee is best brewed around 96°C. The milk – textured (i.e. the frothy stuff on cappuccino or latte) or flat – is best served at around 60°C, but in fact to achieve textured milk, a machine with a steam-wand is ideal. Yes I know, you can buy stand-alone milk heaters and frothers, but top-notch milk-texturing is skillfully achieved by using the steam wand to introduce the right amount of air bubbles.
  • Convenience. You will see that in artisan or pro coffee shops, they are able to pull espresso, texture milk, and server hot water at the same time. This seems to be a time-saver for a busy coffee shop, but in fact it would be difficult to operate in any other way.
  • Consistency. Consistency is such a vital word in the world of coffee, I am surprised we don’t see more talk about it. Consistency of bean freshness, water quality, dosage, tamping pressure, and brewing temperature are really important when making good coffee – consistently. The home barista can control all of those except for the behaviour of the boiler, and is the one “external factor” that the home barista usually needs his or her machine to take care of.

What are the issues?

Many consumer coffee machines have a single boiler (you often see them called “thermoblock”) which keeps the water at the ideal coffee-brewing temperature. But some machines offer a “steam mode” – this basically raises the temperature of the thermoblock to a higher temperature to make steam.

That is all well and good, but this introduces an additional heat-up action between making the coffee and then being able to texture the milk. Why is that not desirable?

  1. Idealy, you want to both make the espresso and texture the milk at the same time. i.e. pull the espresso and add the milk straight away
  2. After making steam, the thermoblock is then too hot to make coffee so it has to cool down. Some machine manufacturers tell you “quick” ways to do that. But it leads to lower levels of consistency
  3. To prepare more than one drink, the time delays between pulling espresso, adding textured milk, pulling the next espresso, etc, can be a pain. If you are making a single cappuccino or latte, then the delay between the end of the coffee pull and ability to add the textured milk is probably OK for the home barista.

The good things about multiple boilers

A coffee machine with more that one boiler (usually 2) will help you deliver fresher and more consistent drinks, more quickly and more easily, with fewer delays or concerns over temperature. In summary, using a dual-boiler machine means:

  • That the two different temperatures for brewing coffee and texturing milk should be more consistent and predictable
  • You can texture your milk at the same time as brewing coffee. Perfect if you like the freshest brew or you have more than one drink to make
  • There is less waiting for the machine to either heat up or cool down

The downside of multiple boilers

The two main issues are cost because a machine with two boilers is inherently more expensive and has higher running costs, and dimensions as a machine with 2 boilers takes up more kitchen space that a similar machine with 1. But cost is the biggie downside in my humble opinion.

Should I buy one?

If you are looking to totally delight your coffee-drinking or gadget-loving partner at Christmas, then one of these machine will do just that!
For the regular coffee drinker (assuming you have textured milk), well probably yes if you can afford the extra cost.
For the dedicated coffee nut or enthusiastic home barista – it would be a great purchase – again if you can afford the higher purchase price.
Finally, these machines tend to be top-notch brands, so you know you are buying a quality machine.

What consumer machines are out there?

We haven’t tested these machines, nor can we justify the cost of buying them to try. But for the consumer, it seems that Sage Appliances lead the way with not just great-looking coffee machines, but with innovation and design. See below a couple of machines that you can research further. If only we had the money here…

Sage by Heston Blumenthal BES980BSUK The Oracle – Black


See more detail…

Also available in steel color

Sage by Heston Blumenthal BES920BSUK The Dual Boiler ™ Espresso Coffee Machine – Black


See more detail…

Also available in steel color