Power factor

Power factor is the ratio of real power (kW) actually doing work to apparent power (kVA) drawn from the electrical supply, with the gap between them caused by the phase lag between voltage and current in inductive loads. A power factor of 1.0 (unity) means all supplied power is usable; facilities with older UPS systems or poorly corrected loads can run as low as 0.7-0.85, forcing operators to size transformers, generators and switchgear for the higher kVA figure rather than the lower kW figure actually billed. Modern double-conversion UPS units typically achieve input power factor above 0.99, and utilities often penalize customers whose power factor falls below about 0.9-0.95 through demand charges or reactive-power surcharges. Because colocation contracts are usually priced per kW, a facility's power factor directly affects how much usable IT capacity a given piece of electrical infrastructure can actually support.