Operation Availabilty versus Operating Rate
Operational availability is the fraction of time a machine functions properly when needed. (Also called operable rate.) The operating rate is the amount of time in a time period (shift, day, etc.) that a machine is used to make something.
Use of an automobile illustrates the difference between the two terms. The operational availability is the percentage of time the car runs properly when needed. The operating rate is the percentage of time per day the car is actually driven.
Lean thinkers use the distinction to illustrate a trap in traditional thinking about efficiency. From a lean perspective, a high operating rate is not necessarily desirable. Whether an operating rate is good or bad depends on whether or not the equipment is producing just what is needed (good) or overproducing (bad). On the other hand, the ideal operational availability is 100% because it refers to how well a machine runs when needed.