My goodness, the Zerno Z1 impressed us from the moment we unboxed it. So much love for detail and craftsmanship has gone into this grinder – it really stands out! We've now tested over 90 espresso grinders. The Zerno Z1 has nothing to hide compared to any other grinder and is undoubtedly one of our top favorites.
You do pay for it, though! In the basic version, it starts at around 1,200 dollars. As always, we also bought the Zerno Z1 at full price. In the end, it came to almost 2,000 dollars, including accessories, grinding burrs, beautiful wooden cladding, and a case.
That's a statement and makes it clear that we're not dealing with a beginner grinder here, but rather a premium-class device. Since the grinder also lives up to this price in terms of content and quality, it's no wonder that my test colleague Michel Indelicato and I discussed at the end of the test series who would be allowed to take the grinder home until the next Home Barista professional course.
Design and Feel: A Solid Block
When the Zerno Z1 sits on the counter, it looks like a statement. It's surprisingly narrow in design, which we rarely see, but it still weighs a hefty 6.5 kilograms. The massive stainless steel base carries the grinder with elegance. Zerno manages this balancing act in every aspect. While other manufacturers of coffee equipment often slip into bulky, blocky design language, with warlike names like "tank" that sum things up accurately, the Zerno looks more like a bird of prey. Powerful, dynamic, aesthetically elegant. The workmanship is seamless, thought through in every detail, and reaches its peak in the grinding chamber.
The 64 grinding burrs are positioned vertically in the grinder and are each screwed in from behind or held magnetically ("Blind Burrs"). They can be removed and changed with just a few simple steps. In my view, the significance of blind burrs is still vastly underestimated. We were able to measure this when another manufacturer switched only one side of the grinding burrs to blind burrs, while the burrs were otherwise the same. Suddenly their main peak narrowed by 30 microns!
We'll get to the particle distribution of the Zerno Z1 later, but I can say this much already: The homogeneity of the Zerno Z1 is spectacular. The entire interior is constructed so that there is barely any room for retention. To this end, Zerno avoids sharp edges inside the grinding chamber. Even the drive pins are rounded and thus empty the chamber very effectively.
The grinder has a modular design. This means that on the one hand, aesthetic elements like wooden covers can be changed, but also technical components like the burr set (auger).
A massive stainless steel dosing cup is supplied, which positions itself magnetically in the correct place under the coffee discharge.
Due to its design, the grinder in its basic configuration is absolutely "aligned," meaning the grinding burrs are parallel to each other and are straight aligned. In order to consistently encounter the same grind size after opening the grinder and to have very well-aligned grinding burrs, we recommend using a torque screwdriver.
The Technology: Slow, But Precise
Inside, a 300-watt motor runs at a constant 900 revolutions per minute. Compared to other grinders, this is rather slow. We measure a grinding speed of approximately 1.0 to 1.1 grams per second. So for a dose of 18 grams, the Zerno Z1 takes about 18 seconds to completely grind empty. That's not a speed record, but with single dosing, quality is our primary concern, not time savings. The slow grinding process combined with the burr sets used has a strong influence on particle distribution, which, along with the blind burrs, explains the high homogeneity of the ground coffee. The burr set also has a slowing effect on the grinding that resembles slow feeding.
What we noticed during operation: The grinder is quite audible at around 81 decibels. Compared to whisper-quiet competitors like an Acaia Orbit, that stands out. It's not an unpleasant sound, but it's noticeable.
Retention and Workflow
The issue of retention is essential in single dosing grinders. We distinguish here between temporary and permanent retention. The temporary retention – that is, what is exchanged between two shots – is an excellent 0.1 to 0.2 grams for the Zerno Z1. That's absolute top class and means you get out almost exactly what you put in.
But we also need to talk about permanent retention. This is ground coffee that settles in crevices and corners and remains there. Here we measure approximately 0.6 grams, which collect mainly behind the grinding burrs and in the discharge area. This is due to the design and a good reason to clean the grinder regularly.
Some coffee collects behind the grinding burrs in the permanent retention area.
Fortunately, Zerno makes it easy for us: With just two screws on the front, the entire grinding chamber can be opened. You have immediate access to the grinding burrs, can brush them out, and reassemble everything. An important note for daily use: When you screw the grinder back together, make sure the screws are tight. If you only tighten them loosely, the grind distance changes, which has direct effects on your espresso.
The grinder tends to build up static charge depending on the bean variety. In these cases, we recommend the Ross Droplet Technique (RDT), that is, a small spray of water on the beans before grinding. This significantly reduces static and ensures that the ground coffee lands cleanly in the cup.
Also excellent is the grind size accuracy and adjustment precision of the grinder. The grind size is expressed as a value in microns. This indicates the distance between the grinding burrs. Interestingly, the displayed grind size is relatively close to our measured x50. If we adjust the grinder to other beverages and then return to espresso, or to the noted grind size, we get the same particle distribution to within a few microns. Long story short: the Zerno Z1 is very well suited for switching between recipes and coffees and then returning to your original coffee.
Taste: Precision Meets Body
Let's get to the most important point: what ends up in the cup? Laboratory particle distribution measurement shows an extremely narrow main peak. The SSP High Uniformity burrs combined with the low rotational speed produce a very homogeneous grind. The X50 value (the median of particle size) is very close to the desired target range, which speaks to high precision.
In terms of taste, this translates into wonderful balance. We tested our "Apas" espresso and were impressed. The espresso shows clear structure. We taste a nice balance between sweetness and bitterness, with notes of nut and nougat, accompanied by a subtle yet distinct stone fruit character. It's not an aggressive acidity, but rather a very well-integrated, bright stone fruit acidity.
At the same time – and this pleasantly surprised us – the espresso has good body. Often, grinders with high clarity lose texture and mouthfeel. The Zerno Z1 manages this balancing act: it delivers flavor differentiation without making the espresso taste thin.
However, the grinder demands skill from the barista. Due to the very homogeneous particle distribution, you need to grind very fine to achieve correct flow times. This means your puck preparation has to be spot on. Sloppy tamping or poor distribution will immediately lead to channeling. Those who work cleanly will be rewarded with excellent results.
Interestingly, the grinder also works very well for filter coffee. When we set the grind size coarse, we get a very clean, almost unimodal grind image that enables clear and structured filter coffees. This is exceptional for pure espresso grinders.
Conclusion: An engineer's dream with a small hurdle
So who is this grinder right for? The Zerno Z1 is not a grinder for the absolute beginner who just wants a quick caffeine fix. It's a precision tool for home baristas who want to understand what burr geometry and pre-breaker design do to taste. It delivers results that compete in the absolute top tier.
Unlike other top-tier single dosing grinders, the Zerno Z1 forgoes the ability to adjust rotational speed (RPM). Instead, the grinder invites you to experiment with different burrs and pre-breakers, and delivers a grind speed of 900 RPM optimized for the pre-breaker. In my view, this makes a lot of sense. When a company like Zerno, which intensively studies burr and pre-breaker geometry, develops around a specific rotational speed, a grinder can be optimized for that.
Does the filter coffee taste good? We only tested that initially and it of course also depends on the burrs used. But we can generally say: yes, the filter coffee we ground and brewed with the Zerno Z1 was among the best filter coffees we've ever had from single dosing grinders.
Despite our enthusiasm for the Zerno Z1, there is a clear "but". Zerno is an American company. For us in Europe, this means: import, customs, and above all, no local service network. If something goes wrong with the motor, you don't just pop the device off to the repair shop around the corner. In the US this is a no-brainer, but here in Europe you need to be aware of this risk. On the other hand, the grinder seems built in a way that technical defects are rather unlikely.
Technically and in terms of taste, we have nothing to fault with the Zerno Z1, quite the opposite. It's solidly built, delivers measurably excellent results, and is fun to use in the workflow – if you're willing to pay the price and overcome the import hurdle. If you already have a good grinder and are looking for that last bit of clarity and nuance, you'll find it here. For us, it remains one of the most exciting grinders we've had on the table recently.
And who gets to take the grinder home? First and foremost, Michel. But the deal isn't bad for Benjamin either. Early in the year, we're hoping to get our hands on the Z2 model, and maybe then that model will find a place next to Benjamin's espresso machine...
