Calculate PUE, the ratio of total facility power to IT equipment power, for a data center.
PUE is the ratio of total facility power to the power actually delivered to IT equipment. A PUE of 1.0 is the theoretical ideal — every watt goes to computing, none to overhead — but is not achievable in practice, since cooling, power distribution losses, and lighting always consume some energy. Most modern facilities fall in the 1.4-1.6 range; hyperscale operators with advanced cooling (free-air, liquid) push below 1.2, while older or poorly optimized facilities can exceed 2.0.
Power Usage Effectiveness
PUE = total_facility_power / IT_power
Data Center Infrastructure Efficiency
DCiE% = (1 / PUE) × 100
1.0 is the theoretical ideal (all power goes to IT, zero overhead) but is unachievable in practice. Values of 1.2-1.4 are considered excellent for modern facilities, 1.4-1.6 is typical/average, and anything above 2.0 signals substantial non-IT overhead worth investigating.
Cooling systems (chillers, CRAC/CRAH units, fans), power distribution losses (transformers, UPS conversion inefficiency, PDU losses), and facility lighting/support systems all consume power without contributing to computing — the sum of these is the 'overhead' that pushes PUE above the ideal 1.0.
DCiE is simply the inverse of PUE expressed as a percentage — it answers 'what fraction of total facility power reaches IT equipment?' A PUE of 1.5 corresponds to a DCiE of about 66.7%, meaning roughly two-thirds of facility power is used productively.