This diagram compares the PID controller with the original mechanical thermostat when making an espresso (which takes approximately 25 seconds, as marked in the diagram).

Noticeable is how long it takes for the thermostat to react on the temperature drop, while the PID controller responds quite quickly. As the diagram shows, the thermostat turnes on at approximately 76 °C. With the PID controller, the temperature never goes below 89 °C. Again, this is measured in the water boiler, not in the group head, where the difference is not as big.

Temperature surfing was used to be able to start brewing at exactly 95 °C with the original thermostat.