According to an example, a method for performing maintenance routines in a plurality of actuators comprises firing a set of actuators at different energies, determining turn on energy values for the set of actuators based on measurements measured via chamber sensors associated with the set of actuators at the different energies, determining turn on energy differences for the set of actuators based on the turn on energy values determined for the set of actuators and threshold turn on energy values associated with the set of actuators, and performing maintenance routines corresponding to the determined turn on energy differences.