Deciding which coffee machine you should buy for home is not easy! There are different types of coffee machines, and it’s important to understand their differences before you even start to compare coffee machine brands. The first step is to decide which type of coffee machine will suit your needs.
Guide to common types of modern espresso coffee machines:
Thermoblock coffee machines
Thermoblock machines are some of the cheapest coffee machines you will encounter. The vast majority of the machines you will see at Myer, David Jones or other retail department stores use thermoblocks. I’m not going to delve into where parts are manufactured, as China actually makes both great and not so great components these days, but suffice to say that thermoblock machines are considered very entry level. These are usually the machine people start out with, until they realise some of the limitations of thermblocks and decide to upgrade to a boiler machine.
What is a thermoblock, and what are the pros/cons?
A thermoblock is basically two plates of metal with thin water channels that run through those plates. The plates heat up quickly as they don’t weigh much and are relatively small. They are cheap to manufacture for this reason also. Unfortunately, their smaller thermal mass is also their downfall in a way. While a large 2L boiler and 4.5kg solid chromed brass group head can maintain a relatively stable temperature, a thermoblock tends to fluctuate, and this can lead to inconsistent shots, or shots where the temperature at the group head is nowhere near ideal.
Remember a difference of just 1 – 2 degrees is all it takes to vastly change the flavour profile of an espresso shot. Ideally, you want the temperature at the group head to be between 92 – 96 degrees, depending on roast depth, coffee origin, dose and a swathe of other factors we may delve into in another blog post.
Aside from temperature stability, the other issue people face with thermoblock machines is poor steam pressure, slowness of the thermoblock in heating up to generate enough steam pressure (with a boiler machine you have steam on tap at any time), and if you only have a single thermoblock machine chances are you can’t even steam while you are extracting a shot of coffee.
Many well known, common household appliance brands use thermblocks.
Single Boiler Heat-exchanger (HX) coffee machines
These are considered a good entry level machine for home use, and while you won’t find many (if any) of these at the department stores, there are plenty of great coffee specialty retailers offering them for sale in Australia, including us here at Ministry Grounds.
What is a single boiler heat-exchanger?
This design has really stood the test of time, and in particular when paired with an e-61 or similar group head with a large thermal mass, is a fantastic home setup. A boiler is essentially a sealed vessel which contains water and a heating element. Since pressure inside a boiler is directly related the temperature, the heating element and a device known as a pressurestat controls when the heating element should be on or off, maintaining a consistent pressure within a narrow margin (often 1.0 to 1.3bar), and temperature.
Adding a heat-exchanger to a single boiler allows the coffee machine to brew coffee and steam milk at the same time. A heat-exchanger is a pipe which runs through the length of the boiler. When you brew a shot of coffee, water runs through this pipe and is heated to the same temperature as the water in the boiler which surrounds the pipe. And thus you can be extracting a shot of coffee via the HX pipe, and taking steam from the boiler at the same time. Since the brew water is not taken directly from the boiler, the water level in the boiler remains almost the same while you are extracting coffee and steaming, again helping to keep temperatures consistent. Small amounts of water does exit the boiler as steam, or when the hot water tap is used, keeping the boiler water fresh.
Water level probes inside the boiler automatically activate the pump when required, to keep the water level within a narrow margin.
Since these machines weigh up to 20kg or more of solid chromed brass and stainless steel, and most of that mass heats up, they are very temperature stable – which is what great espresso is all about! We sell the Expobar e-61 Leva, which uses a 1.5L boiler and is great value at $2,150.
Double boiler coffee machines
A double boiler coffee machine utilises a brew boiler for extracting coffee, and a steam boiler for making all those tasty milk-based coffee drinks. This has both advantages and disadvantages when compared to a single boiler heat-exchanger. The main advantage is each boiler can focus on doing only one task.
The brew boiler can be set to the temperature you require for the coffee you are extracting, and temperatures remain very stable during extracting since there will be no pressure drop due to steaming.
The steam boiler, since it is not delivering brew water and only cares about giving you the best steam, can be set to a higher pressure and temperature, thus enabling faster steaming at higher pressure. While brew boilers often run at 1.0 to 1.3 bar, a steam boiler can often run up to 1.5 bar.
Since dual boiler coffee machines use more parts than simpler heat-exchanger designs, they are often a little pricier. Remember, each boiler needs a heating element, pressurestat, the boiler itself, etc. So now you know the advantages. If you are considering a dual boiler, we sell the Expobar Minore IV, which is considered one of the best value dual boiler e-61 machines on the market! The Minore even has a PID built-in, so that you can manually adjust the temperature of the brew boiler, and pressure in the steam boiler.
Does the size of the boiler matter?
For home use, many people are extremely happy with single boiler HX machines around 1.2L in size. The smaller the boiler, the quicker the machine will heat up, although it’s not a huge difference. A 1.2L boiler will heat up in around 15 mins, while a larger 2L boiler may take 20 mins to reach optimum temperature stability. Heat-up times are not really a problem, since you can use a timer, or just turn the machine on in the morning when you wake up, and by the time you’ve made breakfast it will be ready to go!
Smaller boilers are at a disadvantage in that they hold less steam and water volume, and thus you will run out of steam quicker, meaning the heating element is used more to keep the boiler up to pressure. Fortunately, the heating elements used are quite powerful, and only take a few seconds to bring a small boiler back up to pressure.
A larger boiler will tend to be more stable in general, and thus the heating element doesn’t need to kick in as often. For home use, unless you are a real espresso fanatic and willing to part with serious cash, common boiler sizes from 1.2L up to 2.2L will be fantastic. In a double boiler, each boiler can be slightly smaller, so you might have two 1.5L boilers as in the Expobar Minore.
We hope you’ve enjoyed learning about some of the common types of home coffee machines! You may also be interested in reading our posts on buying and storing roasted coffee, and the amazing new VST filter baskets.
You can buy Expobar coffee machines from us, or feel free to comment below, or contact us if you have any further questions!
I should’ve seen this before posting my article on the site. Now I think I’ve missed quite some good info. Thanks for this, I’ll update our post.
This is the post I’m talking about, very basic stuffs:
Wow thanks, great info. The 9c a shot info makes it even easier to justify upgrading.
Nice write up. I have a few questions.
What are your thoughts on the Rocket Giotto Premium Plus? How does this compare with the Expobar Minore IV? I notice the Rocket has a heat exchanger, but is more exy than the Minore… Is this a branding thing or is the Rocket actually superior?
What uses more power, boiler(s) or thermoblock(s)? Or twin boilers vs a single boiler with a HX?
Are the Minore’s more durable than Sunbeam EM6910′s? My EM6910 has made over 6000 shots of coffee and its starting to pack it in.
Hi Michael,
In the class of machines that we are talking about, there are many heat exchanger machines (HX) – they are single boiler (for steam), with an HX running through the boiler to heat the brew water. It’s a time honoured design that works well (although in the domestic situation the relatively poor temp control means a lot of flushing before you brew if the machine has idled for a while).
The price differences are based on built quality, quality of some components, and cost of the styling side of the design.
The Giotto is a fine machine. But so is the Expobar, the Isomac, etc, etc. In the end it’s largely down to features, style and whatever perception of quality the machine gives off!
While I have a good deal of confidence in Expobar’s build quality, there are certainly nicer looking machine out there, and some will use some components of better quality.
But with any of this class of machine, you will get many, many years of service from them with minimal maintenance. As an example, my Expobar Minore I was bought around six months after they came to Australia, which would make it around 2004 I think. With six coffee-drinking adults at home at the time, it pulled around 15,000 shots before I had it serviced to rectify a couple of leaky seals. Since then, it would have pulled another 6-8,000 shots easily. and I’m thinking I should probably have it checked over again as I think the pressurestat is showing signs of wearing out.
It cost me around $2100 new (not counting the cost of the aftermarket rotary pump conversion I had done later), which means that each shot has cost me around 9c. Pretty good value so far.
As far as power use goes, the boiler machines will use more power heating up from cold, but then relatively little to stay at temp. I strongly suspect that the difference between twin boiler and single boiler/HX is very very small. The twin boilers tend to be smaller, and on the Expobar, the brew water is pre-heated via a short HX before reaching the brew boiler, so it requires only occasional topping up with heat.
Note that a big plus for twin boilers is that the brew temp can be very carefully controlled. In the Minore IV, that is handled with a PID. That is very hard to successfully do on a single boiler HX.
Hope all that helps!