What is available capacity on non-constraint resources beyond what is required to support the constraint called?

• A. Spare capacity
• B. Idle capacity
• C. Excess capacity
• D. Buffer capacity

Answer: (B)

When a bottleneck sets the pace of the system, the other resources often have more capacity than is actually needed to feed that constraint. The portion of their capacity that remains unused while the constraint is being supported is called idle capacity. This idle capacity represents available time that could be used for improvements, maintenance, or absorbing variability, but it isn’t required to keep the constraint running at its maximum throughput.

Spare capacity and excess capacity are related ideas, but idle capacity specifically denotes unused capacity on non-constraint resources that isn’t required to support the bottleneck. Buffer capacity refers to protections against variability, not the unused capacity itself.