What is PUE (Power Usage Effectiveness)?

PUE is the standard metric for measuring data centre energy efficiency. It is calculated by dividing the total facility power consumption by the IT equipment power consumption. A PUE of 1.0 would mean all power goes directly to computing with zero overhead - theoretically perfect but physically impossible. A PUE of 2.0 means the facility uses as much power for cooling, lighting, and other systems as it does for IT. Modern best-in-class hyperscale facilities achieve PUE of 1.08-1.15. Good colocation facilities operate at 1.2-1.4. The industry average is approximately 1.58. Every 0.1 improvement in PUE saves roughly $50,000/year per MW at US average power rates.