If you’re shopping for a new espresso machine, one of the questions you’ll undoubtedly have is which type of machine to go for when it comes to the boiler.
There are single boiler machines, heat exchanger machines, and dual boiler machines.
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Single boiler machines have one boiler ;-), but you’d probably guessed that!
This means that you can’t steam milk and pull a shot at the same time. Also, it means you need to wait a short time in between pulling a shot and steaming milk, due to the temp difference required for each.
If you mainly drink espresso and have little requirement to steam milk, or if you drink milkies but only have one or two per day, then this isn’t really a big deal in my humble opinion.
Entry-level espresso machines such as Gaggia Classic, Sage Barista Express, & Rancilio Silvia plus, bean to cup machines such as Gaggia Brera & De’Longhi ESAM 4200, tend to be single boiler machines.
See my youtube video on Espresso Machines:
Single Boiler Pros
Price. Single boilers are the lowest cost espresso machines.
Single boiler machines will usually be warmed up & ready to pull shots quicker than dual boiler machines.
Single boiler machines (and heat exchanger machines) cost a bit less to run than dual boiler machines.
Single Boiler Cons
Vs heat exchanger and dual boiler machines, the main con for single boiler machines is that you can only do one thing at a time, steam milk or pull the shot.
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Heat exchanger machines allow you to steam milk and pull espresso at the same time, as do dual boiler machines, but they do so via different methods.
Heat exchanger machines, as the name implies, have a heat exchanger system – meaning that heat is borrowed from the steam boiler to heat the brew water.
There’s just one boiler, which is used for steam & hot water, and there’s a copper pipe running through this boiler. Coldwater is pulled through this pipe & heated up to the desired temp for espresso.
Heat Exchanger Pros
Heat exchanger machines (HX machines for short) are usually cheaper because a copper pipe is much cheaper than a second boiler. Heat exchanger machines such as Lelit Mara & Rocket Appartamento, start from around the grand mark, while dual boiler machines tend to start at around double this.
HX machines are generally cheaper to maintain and repair than dual boiler machines, again, because there’s only one boiler.
HX machines use slightly less energy (hence slightly cheaper to run) than dual boiler machines, as there’s only one boiler being heated.
Brew water is fresher with HX machines, as its water is drawn directly from the freshwater reservoir and not from a boiler.
Heat Exchanger Cons
You don’t have direct control over the brew water temperature with HX machines, which means you can’t adjust the steam pressure without impacting on the brew water temp.
You need to perform a cooling flush on HX espresso machines, although many suggest that you should flush double boiler machines before pulling a shot too.
Dual boiler machines, as the name implies, have two boilers, one for coffee, and one for milk.
The obvious example here is the Sage Dual Boiler – although, this isn’t “just” a dual boiler machine! It’s a dual boiler machine that also has a heat exchanger, in order to reduce the thermal shock associated with feeding a boiler with cold water, as the boiler feed is heated via the heat exchanger.
Dual Boiler Pros
Independent control of brew temp and steam temp, meaning that you can adjust the steam pressure without impacting on the brew temp.
Easier to achieve consistent brew temp over a number of consecutive shots.
No need to perform a cooling flush before pulling a shot, although as I mentioned earlier, some baristas insist that the group should be flushed on dual boiler machines too, in order to get the best results.
Dual Boiler Cons
Dual boiler machines tend to cost quite a bit more than heat exchanger machines.
Dual boiler machines tend to cost more to repair and maintain than heat exchanger machines.
Brew water is drawn from a boiler, rather than from a freshwater reservoir.
Dual boiler machines tend to take longer to warm up than HX machines.
So which is the best type of espresso machine for me?
Hopefully, the above info has already given you a good idea of which type of espresso machine is going to work best for you, but if not, here’s a short guide. Ask yourself these questions, and see how many boxes you tick for each, simple :-).
Although it’s worth pointing out that the below tick list is very generalised, and there are new heat exchanger machines being produced that share some of the pros of dual boiler machines.
Best Home Espresso Machines
- Don’t have the budget for HX? (At least around 1k – 1200, including grinder, unless you go down the used route)? Single boiler.
- Want control over steam pressure? DB
- Want to experiment with brew boiler temp? DB
- Don’t have the budget for DB? HX
- Not particularly interested in adjusting steam pressure? HX
- Not particularly fussy about adjusting brew temperature? HX
- Interested in tweaking steam pressure? DB
- Interested in experimenting with brew temp? DB
What about Thermoblock & Thermocoil?
Thermoblocks and thermocoils are essentially heating elements, on-demand water heating systems, an alternative to traditional brew boilers. Think combi boiler vs traditional tank boilers – not quite the same, but similar.
Most of the cheap espresso machines use thermoblocks, which are a block of heated metal through which water is pulsed, being heated as it goes through the chambers.
Some of the more modern, popular espresso machines including the Sage Bambino Plus, Sage Barista Pro, etc., use thermocoils, which aren’t quite the same as thermoblocks.
Check out my review on the Sage Bambino Plus:
Thermocoils are a more modern take on the thermoblock, which has metal tubes coiled within the block, within which the water is circulated. Thermocoils are usually faster, more consistent, and tend to last longer.
Before I sign off, just to add – there’s one thing you can do to upgrade the quality of your coffee regardless of the boiler type, and that is – use better coffee beans :-). Check out my coffee at The Coffeeworks:
Use discount code CBNC25 for 25% off your first order at Coffeeworks
Life is like a box of chocolates, so join my Brew Time list, subscribe to my YouTube Channel, become an accredited coffee botherer (Patreon supporter), try my coffee at The Coffeeworks (use discount code coffeebotherers), follow me on Twitter & Instagram, follow the coffeeblog FaceBook page, and that’s all I have to say about that.