Define capacity factor and explain why renewables often have lower capacity factors than fossil plants.

• A. Capacity factor is actual output divided by potential output at full capacity; renewables depend on weather, causing lower CF.
• B. Capacity factor is the ratio of emissions to capacity.
• C. Capacity factor is the total installed capacity divided by the number of hours in a year.
• D. Capacity factor measures the efficiency of converting fuel to electricity.

Answer: (C)

Capacity factor measures how much electricity a plant actually produces over a period compared to how much it could produce if it ran at full nameplate capacity for the same period. In formula form, CF = energy produced during the period ÷ (nameplate capacity × time). Over a year, that’s energy produced in a year divided by (P_nameplate × 8760 hours). Renewables often have lower capacity factors because their output depends on weather—sunlight for solar and wind for turbines—so they can’t run at full capacity continuously. Fossil-fueled plants, with a steady fuel supply, can operate more consistently near their full capacity, leading to higher capacity factors on average. The option that defines capacity factor as total installed capacity divided by the number of hours in a year isn’t the correct definition and doesn’t reflect the actual-versus-possible-output idea.