Grinding generates heat through friction, and how much it matters depends entirely on volume.
What happens at home
An 18 g dose takes 8 to 12 seconds. The burrs warm slightly and the grounds leave at close to room temperature.
Measured temperature rises of a few degrees are typical. That is not enough to drive off aromatics meaningfully.
For a home user, this is not a real problem.
Where it does matter
Commercial grinders running continuously. Burrs reach genuinely high temperatures over a busy service, and the last dose of a rush behaves differently from the first.
This is why commercial grinders have large burrs — more mass, more surface, better heat dissipation — and why some have cooling fans.
Very large flat burrs at home, ground back to back, can warm up over several consecutive doses.
The secondary effect
Heat changes grind behaviour more than it changes flavour. Warm burrs sit at a marginally different effective gap, so shot times can drift over a session.
If shots creep faster after four in a row, this is a plausible cause.
What actually causes stale-tasting grounds
Retention, not heat. Grounds left in the chamber overnight are stale by morning.
Grinding ahead of time. Ground coffee degrades in minutes.
The practical answer
Do not worry about grinder heat at home. Do worry about retention and about grinding immediately before brewing.
Last reviewed 8 August 2026