Diesel generators are often used as standby units at capacities of about ____.

• A. 5 MW
• B. 50 MW
• C. 1 MW
• D. 10 MW

Answer: (A)

Standby diesel generators are sized to carry the essential loads of a facility during an outage. For many utility substations and industrial applications, a common standby capacity is in the megawatt range, with five megawatts being a typical standard size. This amount of power is large enough to keep critical systems—like control houses, protection relays, communications gear, and important switching equipment—operating, while still being cost-effective and manageable to install and maintain. A much larger unit, such as ten or fifty megawatts, would be more than what’s needed for standby duties and would resemble a small peak or prime-power plant. A one-megawatt unit is plausible for smaller facilities, but it doesn’t reflect the usual sizing used for standby in many larger-scale applications. Thus, five megawatts is a representative standby capacity.