Explain peak demand and how it differs from peak load.

• A. Peak demand is instantaneous power; peak load is the daily average.
• B. Peak demand is the maximum electricity demand over a period; peak load is the highest instantaneous power required at a moment.
• C. Peak load occurs monthly; peak demand yearly.
• D. They are synonyms.

Answer: (B)

The main idea is distinguishing a time-bounded maximum from an instant maximum. Peak demand refers to the highest amount of electricity that customers collectively require over a defined period, such as a month or year. Utilities look at this period-wide maximum because it shows the size of capacity the grid must be prepared to supply during that interval, and it often drives demand charges.

Peak load, on the other hand, is the highest instantaneous power required at any single moment. It’s about the real-time rate of energy use—the peak moment when the system experiences its largest single spike in demand.

So, a hot afternoon might cause a sharp, brief spike in power use (the peak load), and that same spike could define the maximum demand observed over the billing period (the peak demand) if it’s the largest value recorded during that period. The other statements mix up instantaneous versus period-based maxima and aren’t consistent with how these terms are used.