In power systems, what term describes the ability to supply the aggregate electrical demand without failure?

• A. System reliability
• B. System efficiency
• C. System stability
• D. System capacity

Answer: (D)

Understanding this asks for the measure of how much power the system can deliver given its resources. The phrase “ability to supply the aggregate electrical demand without failure” points to the system’s overall capability to meet load with no outages, which is captured by system capacity—the total amount of power the grid can deliver under operating limits, including a safety margin.

The other terms refer to different aspects: efficiency is about minimizing losses in generation and transmission, stability is about staying in a steady operating state after disturbances, and reliability is about the likelihood of meeting demand without outages over time. While reliability relates to outages in a probabilistic sense, the description here directly maps to the system’s capacity to supply the load.