WPM ZP-1 Review – A Very Good Single Dosing Grinder!

The WPM ZP-1 is a single dosing espresso grinder priced at 1,140 euros / 1,180 CHF. WPM is based in Hong Kong, has been active in the milk pitcher segment for years, and has built a name for itself with thermoblock espresso machines. The ZP-1 is its first attempt at a grinder for the European market. As with all our grinders, we bought it ourselves and ran it through our testing protocol. The result: the ZP-1 does several things really well. But at 1,140 euros, it's fair to ask what you're getting here that you couldn't get elsewhere for less.

Overhang, and a dial that's genuinely fun to use

The ZP-1 weighs 8 kg, is about 13 cm wide, 27 cm deep, and a good 30 cm tall. The housing leans forward noticeably, giving the grinder a distinct overhang. Whether that works visually 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 sub-marks each, and adjusts steplessly. It's one of the best adjustment dials we've ever tested. In use, it has a natural, pleasant resistance that allows for very fine corrections. Minor criticism, though: the pointer isn't positioned quite optimally, and the gaps between the sub-marks are wide enough that you actively have to work with the in-between zones. For a dial of this size and ambition, more subdivisions would make sense.

The chute is magnetically detachable. In terms of premium feel, it's the one part of the grinder that falls slightly short. It's made of plastic, which only becomes noticeable once you take it off — otherwise it has the same coating as the rest of the grinder. The manufacturer states that the plastic chute reduces static buildup.

The built-in knocker works well and makes a bellows unnecessary. It's reliable with light and medium roasts. With dark roasts, a bit more sticks to the walls.

Buy the WPM ZP-1

🛠️ Where to buy in Germany and Austria [Partner link]*: Bohnendealer

*We look for specialty partners on your behalf whom we know deliver good work and good service. We stay in close contact with these retailers. These are commission links. If you order through this link, it doesn't cost you anything extra, but we receive a small commission, which we put toward new test equipment. We're continuing to work on this and are looking for capable partners for you across the DACH region.

Grinding mechanism and cleaning. The best we've seen so far

64 mm flat burrs sit inside the grinding mechanism — more precisely, 63.8 to 63.9 mm, which means SSP burrs don't fit directly. WPM includes an adapter that lets you mount SSP burrs.

The RPM control ranges from level 1 (600 rpm) to level 10 (1,300 rpm). We'll get to what that means for particle distribution further below.

When it comes to cleaning, the ZP-1 sets a new benchmark that, so far, nothing else has matched. With just a few motions, and without touching the grind setting, you're inside the grinding chamber. No tools, no screws to turn, no settings to memorize. Pop it open, brush it out, put it back together. By the way, you can reach for the cleaning agent here far less often than with grinders whose chambers you're reluctant to open in the first place.

Grinding speed and noise level

The ZP-1 grinds 21.5 g in 10 seconds — a medium-fast grind. For 18 g, the grinder needs 12 seconds. Not a record, but not an everyday annoyance either. The grind time gives you a moment to put the lid on, which drops 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 on, which falls into the quiet category. Excellent.

Grinding temperature and consistency

The first sample comes in at 31.3 °C; after five consecutive grinds with 20-second pauses in between, the grounds rise to 32.6 °C. The average sits at 32.02 °C. That's good. Even light, aromatically sensitive roasts aren't put under thermal stress, and anyone pulling several espressos back to back doesn't need to worry about a temperature issue.

Consistency is equally convincing. A standard deviation of 0.11 g across 15 grinds is very good. Anyone relying on reproducible recipes will find a solid foundation here.

Retention. Remarkably little for this chamber size

Anyone opening up the ZP-1's grinding chamber for the first time might get a little worried. The space around the burrs is generous, and visually you wouldn't be surprised by retention of more than a gram. The measurement comes out at 0.5 g temporary, 0.2 g permanent, 0.7 g absolute. That's very good.

0.5 g of temporary retention means that every grind carries along half a gram from the previous one. Barely noticeable in everyday use. If you're switching between light and dark beans, running two or three purge shots through gets you a clean transition. The permanent retention of 0.2 g is minimal and not a concern for the grinder's flavor environment. The fact that the ZP-1 holds this value despite its generous chamber size is a solid piece of engineering.

Grind-setting repeatability

In our adjustment test (espresso, ristretto, lungo, back to espresso), the ZP-1 shows one quirk. The x50 value at the starting setting (T4) is 254.6 µm; after returning to it (T7), it's 225.9 µm — a difference of nearly 29 µm. At the same time, the fines fraction rises from 28.7% to 35.3%. So the grinder returns to roughly the right range, but doesn't land on exactly the same spot.

However, since a repeated T4 measurement (T4-1, T4-2) at different RPM settings produces almost exactly the same particle distribution, we consider the T7 measurement an outlier. We also had no trouble finding our way back to the exact grind setting when adjusting between recipes ourselves.

Particle distribution. Broadly spread, RPM without effect

We analyze particle distribution in cooperation with ZHAW Zurich, using the Retsch Camsizer X2.

At the espresso setting (T4, RPM 5.5), the x50 value is 254.6 µm, the fines fraction (Qf <100 µm) is 28.7%, and the 60% main peak width is 230.7 µm.

A fines fraction of 28.7% falls in the mid-to-lower range. The resulting cup is transparent, the acidity comes across cleanly structured, and body stays somewhat restrained.

The main peak width of 230.7 µm sits in an interesting sweet spot that grinds both light and darker roasts reliably. For very light roasts, where maximum clarity is the goal, switching to SSP burrs would be a good move.

RPM comparison. We took separate particle-distribution samples at RPM 1 (600 rpm) and RPM 10 (1,300 rpm), with the recipe dialed in at 18 g in, 45 g out, 25 seconds. The main peak width stays nearly identical: 233.6 µm at RPM 1, versus 231.0 µm at RPM 10. Unlike other variable-speed grinders, where the RPM setting noticeably shifts the particle distribution, the ZP-1 with its stock burrs shows barely any effect. The RPM function is there, but with the standard burrs it changes almost nothing.

Cupping

For the particle-distribution measurements and all grind samples, we use our usual 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, to show what the ZP-1 gets out of light-roasted coffees. The acidity was cleanly structured, the finish long and fruity. Not an espresso with a lot of body, but a balanced, highly transparent shot — exactly what you'd expect given the moderate fines fraction of 28.7%.

Technical specs at a glance

* Prices incl. VAT, as of January 2026.