Efficiency is a ratio of produced power over used input. It represents how efficiently is input product converted to mechanical power. If the shaft is overloaded, some produced power will be wasted and efficiency will go down accordingly. There is also loss of efficiency when the machine is starting-up. To avoid startup losses, this machine should run continuously without interruption.
When enabled, the turbine will be automatically paused once the shaft is nearly fully charged to save the input product from being wasted. The production will resume once the shaft's charge gets low. Keep in mind that when turbine starts, it takes it some time to get to the full power.