How much pressure should espresso machines generate during extraction?

The optimal pressure for espresso extraction is generally considered to be around 9 bars. This pressure strikes a balance that allows water to pass through the coffee grounds effectively, ensuring that the flavors and oils are extracted properly while preventing over-extraction, which can lead to bitterness. At 9 bars, the espresso machine can create a rich, concentrated shot with the characteristic crema on top, which is essential for a great espresso experience.

While other pressures, such as 6 bars, may be too low for proper extraction, and pressures above 12 or 15 bars may lead to over-extraction or cause the machine to work inefficiently, 9 bars represents an industry standard recognized by coffee professionals for achieving the best flavor profile in espresso.