Power Usage Effectiveness (PUE) is a data-center efficiency metric that compares total facility energy use to the energy used by IT equipment alone. A PUE of 1.0 would mean all power goes directly to servers, storage, and networking; in practice, anything above 1.0 reflects overhead such as cooling, power conversion, UPS systems, lighting, and distribution losses.
PUE matters in cyber security because compute capacity is part of operational resilience. A poorly efficient site costs more to run, leaves less headroom for growth, and can become harder to defend when cooling or power systems are stressed. Security teams use PUE during vendor selection, capacity planning, and risk reviews to judge whether a facility can support sensitive workloads reliably. Sudden changes in energy use can also help operators spot abnormal load, such as runaway processes, misconfiguration, or unauthorized compute activity.