Of the below, which is a power efficiency indicator?

Power Usage Effectiveness (PUE) is the most widely recognized and adopted energy efficiency indicator for data centers globally and is emphasized heavily within the EPI sustainability framework. PUE measures how effectively a data center uses power and is calculated by dividing theTotal Facility Powerby theIT Equipment Power. The purpose of this indicator is to show how much of the energy consumed by the facility actually reaches IT equipment (servers, storage, network gear) versus how much is consumed by support infrastructure such as cooling, UPS losses, lighting, and building systems.

A lower PUE indicates a more efficient data center, with values approaching 1.0 representing ideal efficiency—where nearly all consumed power is being used for IT load. PUE is essential for benchmarking, energy-saving initiatives, identifying efficiency improvement opportunities, and measuring the success of infrastructure optimization projects. The other options listed—nil, w; CPU; and uw—are irrelevant to facility energy efficiency metrics. CPU relates to computing processors, not facility efficiency; the others are incorrect units or meaningless terms in this context.

Thus,PUEis the correct and industry-standard power efficiency indicator.