Short Description
Critical IT load refers to the actual computing equipment inside a data center — the servers, GPUs, storage, and networking gear that perform core workloads. It’s the portion of power that directly feeds the infrastructure tenants care about. Gross load, by contrast, refers to the total facility power consumption under full load, including all supporting infrastructure like cooling, power distribution, and lighting.
PUE (Power Usage Effectiveness) is a metric that measures how efficiently a data center delivers power to its critical IT load. A PUE of 1.0 means every watt goes directly to computing; higher values reflect overhead like cooling, power distribution, and lighting. You can roughly calculate PUE by dividing gross load (total facility power draw) by critical IT load. For example, if a site draws 100MW in gross load and 80MW goes to critical IT, the PUE would be 100 ÷ 80 = 1.25.
However, there’s nuance to this math — particularly around how overbuilding and peak load planning affect these figures — which is explored in more detail below.