What is power budget/derating?

• A. Measuring energy efficiency of a server under peak load.
• B. Setting a maximum power limit in BIOS.
• C. Tracking power usage per component for auditing.
• D. Ensuring the PSU and rack PDU capacity can supply worst-case server draw with headroom.

Answer: (D)

Power budget and derating focus on sizing the electrical system to support the maximum possible load, with a safety margin. In practice, you estimate the worst-case current a server could draw and verify that the power supplies (the server’s PSU) and the rack’s PDUs can deliver that amount under real conditions, leaving headroom for variations. Derating means applying a factor to account for conditions that reduce usable power—like higher ambient temperatures, aging hardware, and efficiency losses—so you don’t rely on the device’s nominal rating as-is. This approach prevents outages by guaranteeing the infrastructure can handle peak demand with some margin.

That’s why the best choice describes ensuring the PSU and rack PDU capacity can supply worst-case server draw with headroom. The other options focus on efficiency testing, per-server power caps, or usage auditing, which aren’t about designing the capacity of the electrical infrastructure.