The **peak power output** of an electrical system is the maximum instantaneous power it can deliver under load. In data center design, this figure determines the upper bound of what the entire power chain — from utility feed through [[UPS Batteries|UPS]], [[Single Line Diagram|switchgear]], and [[Power Infrastructure|PDUs]] — must be rated to handle without tripping breakers or degrading equipment. --- ### **First Principle: Design for the peak, pay for the average.** Electrical infrastructure must be sized to survive worst-case demand spikes, even though the facility operates well below that ceiling most of the time. Under-provisioning for peak leads to cascading failures; over-provisioning wastes capital. --- ### Key Considerations - **Peak vs Sustained Load**: A GPU cluster may draw 80% of rated power during training but spike to 100% during checkpoint writes or all-reduce operations. The power chain must tolerate the spike, not just the average. - **Inrush Current**: When servers or cooling systems start up simultaneously, momentary current draw can exceed steady-state by 2–5×. Circuit breakers, UPS systems, and generators must account for this. - **Derating**: Equipment is typically derated to 80% of nameplate capacity for continuous operation, meaning a 100 kW UPS should only be loaded to 80 kW sustained. - **Relationship to [[RMS]]**: RMS power gives the effective continuous power, while peak power represents the instantaneous maximum. Both must be understood to size infrastructure correctly. --- ### Actionable Insights When specifying power infrastructure for a [[Modular Data Center Design Principles|modular data center]], always calculate peak power draw per rack under worst-case workload conditions — not just average utilisation. This means profiling actual GPU and CPU workloads under load, not relying on manufacturer TDP alone. The gap between peak and average determines how much headroom is needed in the [[Single Line Diagram|power chain]] and how aggressively you can oversubscribe power capacity across racks. --- ### In the Data Center Context | Metric | Typical Range | Why It Matters | |--------|--------------|----------------| | Peak-to-average ratio | 1.1–1.4× | Determines required headroom | | Derating factor | 80% of nameplate | Safe continuous loading | | Inrush multiplier | 2–5× steady state | Breaker and UPS sizing | [[Power Infrastructure]] | [[RMS]] | [[IT Load]] | [[Rack power Density]] | [[Power Usage Effectiveness - PUE]]