Certainly not at the setpoint. In t

Certainly not at the setpoint. In the example given it will stabilize at
some steady state level below the setpoint. This steady state deviation is
known as offset and is inherent in all proportional control systems.
Despite this obvious disadvantage, (we cannot return the process to the
setpoint after a disturbance with proportional control) this mode of
control will form the basis for all our control strategies. In the next
section we will discuss a more practical control scheme using
proportional control and also ways of lessening the problem of offset.