WPM ZP-1 Review - Excellent Single Dosing Grinder!

The WPM ZP-1 is a single-dosing espresso grinder priced at 1,140 Euros / 1,180 CHF. WPM, based in Hong Kong, has been active in the milk pitcher segment for years and has made a name for itself with thermoblock espresso machines. The ZP-1 is their first grinder attempt on the European market. Like all our grinders, we purchased it ourselves and put it through our test protocol. The results: The ZP-1 does several things really well. But at 1,140 Euros, one might ask what you get that you couldn't get cheaper elsewhere.

Overhang and a wheel that's fun to use

The ZP-1 weighs 8 kg, is approximately 13 cm wide, 27 cm deep, and a good 30 cm high. The casing is sharply angled forward, and the grinder has a noticeable overhang. Whether this is aesthetically pleasing is a matter of taste.

The grind adjustment wheel is not a matter of taste. It is oversized, precisely engraved with 30 main numbers and 4 sub-markings each, and steplessly adjustable. One of the best adjustment wheels we have ever tested. In operation, you feel a natural and pleasant resistance that allows even the finest corrections. A minor criticism, however: The pointer arrow is not perfectly aligned, and the distances between the sub-markings are so large that one must actively use the intermediate areas. For a wheel of this size and claim, more subdivisions would be useful.

The exit spout is magnetically removable. In terms of premium feel, it is the only element of the grinder that falls somewhat short. It is made of plastic, which is only noticeable when removed. Otherwise, it is coated exactly like the rest of the grinder. The manufacturer states that the plastic spout reduces static charge.

The integrated knocker works well and eliminates the need for a bellows. It works reliably with light and medium roasts. With dark roasts, slightly more grounds stick.

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Burrs and Cleaning. The best we've experienced so far

64 mm flat burrs are in the grinder, more precisely 63.8 to 63.9 mm, which means SSP burrs do not fit directly. WPM provides an adapter for mounting SSP burrs.

The RPM control ranges from level 1 (600 rpm) to level 10 (1,300 rpm). What this means for particle distribution will be discussed below.

When it comes to cleaning, the ZP-1 sets an unprecedented standard. In just a few steps, without adjusting the grind size, you can access the grinding chamber. No tools, no unscrewing, no remembering settings. Done, open, brush out, reassemble. By the way, you can use cleaning agents much less often here than with grinders where you are reluctant to open the grinding chamber.

Grind speed and noise level

The ZP-1 grinds 21.5 g in 10 seconds, which is a medium-fast grind. For 18 g, the grinder takes 12 seconds. Not a record, but also not an everyday annoyance. The grinding time gives you time to put the lid on, which reduces the noise level from 85 to 80 decibels (at 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.

Grind temperature and consistency

The first sample is at 31.3 °C, after five consecutive grinds with 20 seconds pause each, the ground coffee rises to 32.6 °C. The average is 32.02 °C. This is good. Even light, aromatically sensitive roasts are not thermally stressed, and anyone brewing several espressos in a row will not have a temperature problem to worry about.

Consistency is also convincing. A standard deviation of 0.11 g over 15 grinds is very good. Those who rely on reproducible recipes will find a reliable basis here.

Retention. Surprisingly little for this construction space

Anyone who sees the ZP-1's grinding chamber open for the first time will be concerned. The space around the burrs is generous; visually, a retention of more than a gram would not be a surprise. The measurement shows 0.5 g temporarily, 0.2 g permanently, 0.7 g absolutely. That is very good.

0.5 g temporary retention means that with each grinding process, half a gram from the previous pass is included. Barely noticeable in everyday use. Those who switch between light and dark beans grind two to three purge beans, then the transition is clean. The permanent retention of 0.2 g is minimal and uncritical for the aroma climate in the grinder. The fact that the ZP-1 maintains this value despite the generous construction space is a respectable engineering achievement.

Grind setting repeatability

In the adjustment test (espresso, ristretto, lungo, return to espresso), the ZP-1 shows a peculiarity. The x50 value of the initial setting (T4) is 254.6 µm, after returning (T7) it is 225.9 µm, a deviation of almost 29 µm. At the same time, the fines content increases from 28.7 % to 35.3 %. The grinder therefore returns to the correct range, but does not hit exactly the same position.

However, since we achieve almost exactly the same particle distribution with repeated T4 measurements (T4-1, T4-2) at different RPMs, we consider the T7 measurement an outlier. We also had no difficulty finding the exact grind setting again when adjusting recipes.

Particle distribution. Broadly positioned, 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 fines content (Qf <100 µm) is 28.7 %, and the 60% main peak width is 230.7 µm.

A fines content of 28.7 % is in the medium to lower range. The cup is transparent, the acidity is clearly structured, and the body is rather subdued.

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 desired, opting for SSP burrs would be a good step.

RPM comparison. We took separate PVM samples at RPM 1 (600 rpm) and RPM 10 (1,300 rpm), adapting the recipe to 18 g in, 45 g out, 25 seconds. The main peak width remains almost identical, at 233.6 µm for RPM 1 and 231.0 µm for RPM 10. Unlike other grinders with variable speed, where the RPM setting significantly shifts the particle distribution, the ZP-1 with its factory burrs shows hardly any effect. The RPM function is present, but changes little with the standard burrs.

Tasting

For the PVM measurements and all grind samples, we always use our reference coffee, 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 shows what the ZP-1 brings out of light roasted coffees. The acidity was clearly structured, the aftertaste long and fruity. Not an espresso with a lot of body, but a balanced shot with a lot of transparency, exactly what the moderate fines content of 28.7% suggests.

Technical data at a glance

* Prices incl. VAT, as of January 2026.