The WPM ZP-1 is a Single Dosing espresso Kaffeemacher for €1,140 / CHF 1,180. WPM comes from Hong Kong, has been active in the milk jug segment for years, and has made a name for itself with thermoblock espresso machines. The ZP-1 is their first grinder venture on the European market. Like all our grinders, we purchased it ourselves and put it through our test protocol. What came out: The ZP-1 does several things really well. But at €1,140, you can ask what you're getting that you couldn't get cheaper elsewhere.
Overhang and a dial that's fun to use
The ZP-1 weighs 8 kg, is roughly 13 cm wide, 27 cm deep, and just over 30 cm tall. The housing is strongly tilted forward, and the grinder has noticeable overhang. Whether that looks right is a matter of taste.
The grind adjustment dial is not a matter of taste. It's oversized, precisely engraved with 30 main numbers and 4 subdivisions each, and infinitely adjustable. One of the best adjustment dials we've ever tested. During operation, you feel a natural and pleasant resistance that also allows for the finest corrections. Minor criticism though: The pointer arrow doesn't sit quite optimally, and the spacing between the subdivisions is so large that you have to actively use the areas in between. For a dial this size and with these ambitions, more subdivisions would make sense.
The discharge chute is magnetically removable. In terms of high-quality appearance, it's the only element of the grinder that falls a bit short. It's made of plastic, which is only noticeable when you remove it. Otherwise, it's coated exactly like the rest of the grinder. The manufacturer states that the plastic discharge creates less static electricity.
The integrated knocker works well and eliminates the need for a bellows. It functions reliably with light and medium roasts. With dark roasts, a bit more sticks.
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Grinding mechanism and cleaning. The best we've ever experienced
64 mm flat burrs are housed in the grinding mechanism, more precisely 63.8 to 63.9 mm, which means that SSP discs don't fit directly. WPM supplies an adapter with which SSP discs can be mounted.
The RPM adjustment ranges from level 1 (600 RPM) to level 10 (1,300 RPM). We'll explain what this means for particle distribution further down.
When it comes to cleaning, the ZP-1 sets a standard that has been unmatched so far. In just a few simple steps, without adjusting the grind setting, you have access to the grinding chamber. No tools, no screwing, no settings to remember. Snap, open, brush out, reassemble. By the way, you need to use cleaning agent much less frequently here than with grinders where you're reluctant to open the grinding chamber.
Grinding Speed and Noise Level
The ZP-1 manages 21.5 g in 10 seconds, which is a medium-fast grind. For 18 g, the grinder needs 12 seconds. Not a record, but not an everyday annoyance either. The grinding process gives you time to put the lid on, which reduces the noise level from 85 to 80 decibels (in the case of the highest RPM). At RPM 1, it's 80.8 dB(A) or 75 dB(A) with the lid, which falls into the quiet category. Excellent.
Grinding Temperature and Consistency
The first sample is at 31.3 °C; after five consecutive grinds with 20-second intervals, the ground coffee rises to 32.6 °C. The average is 32.02 °C. That's good. Even light, aroma-sensitive roasts are not thermally stressed, and if you pull multiple espressos in succession, you won't have to worry about temperature issues.
Consistency is also convincing. A standard deviation of 0.11 g over 15 grinds is very good. Anyone who depends on reproducible recipes will find a reliable foundation here.
Retention. Surprisingly little for this space
The first time you see the ZP-1's grinding chamber open, you get worried. The space around the discs is generous; visually, a retention of more than one gram wouldn't be a surprise. Measurement reveals 0.5 g temporarily, 0.2 g permanently, 0.7 g absolutely. That's very good.
0.5 g temporary retention means that with each grinding process, half a gram from the previous batch is included. Barely noticeable in everyday use. If you switch between light and dark beans, you grind through two or three purge beans, then the transition is clean. The permanent retention of 0.2 g is minimal and non-critical for the aroma climate in the grinder. That the ZP-1 maintains this value despite the generous space is solid engineering.
Grind Setting Replicability
In the adjustment test (espresso, ristretto, lungo, return to espresso), the ZP-1 shows a special characteristic. The x50 value of the initial setting (T4) is 254.6 µm; after the return (T7) it's 225.9 µm—a deviation of just under 29 µm. At the same time, the fine fraction increases from 28.7% to 35.3%. So the grinder returns to the correct range but doesn't hit exactly the same position.
However, since we achieved almost exactly the same particle distribution in repeated T4 measurements (T4-1, T4-2) with different RPMs, we consider the T7 measurement an outlier. When adjusting between recipes, we also had no difficulty finding the exact grind setting again.
Particle Distribution. Broad-based, RPM without effect
We analyze the particle distribution in cooperation with ZHAW Zurich using the Retsch Camsizer X2.
In the espresso setting (T4, RPM 5.5), the x50 value is 254.6 µm, the fine fraction (Qf <100 µm) is 28.7%, and the 60% main peak width is 230.7 µm.
A fine fraction of 28.7% is in the medium to lower range. The cup turns out transparent, the acidity is clearly structured, body is rather restrained.
The main peak width of 230.7 µm is in an interesting sweet spot that reliably grinds both light and darker roasts. For very light roasts, where maximum clarity is required, switching to SSP discs would be a good step.
RPM Comparison. We took separate PVM samples at RPM 1 (600 RPM) and RPM 10 (1,300 RPM), adjusting the recipe to 18 g in, 45 g out, 25 seconds. The main peak width remains nearly identical—233.6 µm at RPM 1 and 231.0 µm at RPM 10. Unlike other grinders with variable speed, where the RPM setting noticeably shifts the particle distribution, the ZP-1 with its factory burrs shows hardly any effect. The RPM function is present but barely changes anything with the standard discs.
Tasting
For the PVM measurements and all grinding samples, we use our reference Kaffeemacher, the Apas Espresso, a natural processed Brazilian coffee from the APAS cooperative. In the video we brewed Yulieth, a washed Pink Bourbon from Colombia, which demonstrates what the ZP-1 brings out of light roasted coffees. The acidity was clearly structured, the aftertaste long and fruity. Not an espresso with lots of body, but a balanced shot with plenty of clarity—exactly what the moderate fine fraction of 28.7% suggests.
Conclusion. Very good overall package with an open question
The ZP-1 is a well-thought-out, solid single-dosing grinder. With its size, the grind adjustment wheel ranks among the best we've had on the table. Accessibility to the grinding chamber is simply unmatched. Retention is very low despite the large space. Thermal stability is convincing.
Strengths
- Grind adjustment wheel precise, stepless, pleasant to use
- Cleaning: fastest access to the grinding chamber we've ever tested
- Absolute retention 0.7 g, very good for this space
- Grinding temperature 32 °C, thermally unproblematic
- Low static, interesting particle distribution suitable for many roasts
Weaknesses
- RPM function without measurable effect on particle distribution (with factory burrs)
- Grind setting replicability between T4 and T7 not reproducible, likely due to the coarse detents and the distant arrow
Who is the WPM ZP-1 suitable for? Anyone looking for a high-quality single-dosing grinder, works daily with light to medium roasted coffees, and experiences cleaning not as a tedious chore but as a quick step will be well served by the ZP-1. For frequent bean switchers, 0.7 g retention is more than sufficient.
Who is it not suitable for? For us, it remains unclear what justifies the 1,140 euro purchase price when similar grinding discs and particle distributions are sometimes available for 500 to 800 euros. And grinders like the Timemore models (64 and 78) offer light roast enthusiasts a more interesting grind distribution right out of the box.
One thing is clear in any case: the quality of the ZP-1 speaks for itself.
We purchased our WPM ZP-1 model from jeronimo kaffee in Switzerland.
Test Results: WPM ZP-1
Ratings according to the KM Test Protocol for Espresso Grinders. All measurements taken by ourselves. We measure volume according to protocol with the lid on, here at RPM 10. At RPM 1 it is 75.2 dB and thus a green value. Particle distribution does not have its own line because it is expressed in the espresso potential.
Technical Specifications at a Glance
| Property | Value |
|---|---|
| Price | 1,140 EUR / 1,180 CHF (as of January 2026) |
| Burr Size | 64 mm (63.8–63.9 mm) Flat Burr |
| Operating Mode | Single Dosing |
| Grinding Speed | 21.5 g / 10 Sec | 12 Sec for 18 g |
| Volume | 80.8 dB(A) (RPM 1) | 85.2 dB(A) (RPM 10) |
| Grinding Temperature | 31.3–32.6 °C (first to last sample) |
| Absolute Retention | 0.7 g (of which 0.5 g temporary, 0.2 g permanent) |
| Consistency (Std Dev) | 0.11 g |
| x50 (Espresso T4, RPM 5.5) | 254.6 µm |
| Fine Fraction Qf <100 µm (T4) | 28.7 % |
| 60% Main Peak Width (T4) | 230.7 µm |
| RPM Control | Yes, Levels 1–10 (600–1,300 RPM) |
| Weight | 8 kg |
| Dimensions (W × D × H) | approx. 13 cm × 27 cm × 30 cm |
| Special Features | Integrated knocker, instant grind chamber accessibility, magnetic dosing cup, SSP via adapter possible |
* Prices incl. VAT, as of January 2026.
