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Boiler types: single, heat exchanger & dual boiler

The boiler design is the single biggest architecture choice on an espresso machine — it decides whether you can brew and steam at once, how stable your temperature is, and a lot of the price.

PID temperature control

A PID holds brew temperature within a tight band instead of letting it swing with a simple thermostat — one of the biggest levers on shot consistency.

Pre-infusion

A gentle wetting of the coffee puck before full pressure, which can improve evenness, reduce channeling and sweeten the cup.

The E61 group head

A classic commercial-style brew group, prized for temperature stability and built-in mechanical pre-infusion — and found on a huge range of prosumer machines.

Portafilter size (58mm and others)

The basket diameter of the portafilter; 58mm is the commercial standard, with 54mm and 57mm on some home machines — and it affects which accessories fit.

Nine bar brewing pressure

Espresso is traditionally pulled at around 9 bar of pressure; many machines ship higher and benefit from being tuned down, and some let you vary pressure during the shot.

Flat vs conical burrs

The two main grinder burr geometries. They grind differently and many tasters associate them with different cup characters — though neither is strictly better.

Single dosing

Grinding one shot at a time from a weighed dose of beans, instead of keeping a hopper full — better freshness and easy coffee switching, but it needs a low-retention grinder.

Grind retention

How much ground coffee stays trapped inside the grinder between doses — the lower the better, especially if you single dose.

Dialing in a shot

The process of adjusting grind size, dose and time to hit a target ratio and taste — the core skill of home espresso.