Data Center Electrical Sizing Calculator
Turn a kW load into three-phase amperage, apply the NEC continuous-load rule, and get first-pass UPS and generator sizing.
kW×1000 ÷ (√3 × V × PF)
NEC 80% continuous rule (÷0.8)
kVA with headroom
kW with headroom
Results update live as you type. For planning and field-check estimates — always verify against applicable standards and equipment ratings.
Sizing the electrical backbone
Three-phase current follows one formula: amps = watts ÷ (√3 × line voltage × power factor). At 480 V and 0.95 PF, a 500 kW load draws about 633 A. But the number you design conductors and breakers around is larger: the National Electrical Code treats data center loads as continuous (three hours or more), and NEC 210.20/215.3 require overcurrent devices to be sized so the continuous load doesn't exceed 80% of the rating — equivalently, dividing your calculated amps by 0.8.
UPS systems are rated in kVA, so the kW load is divided by power factor before headroom is added; a 20–30% margin covers load growth, battery aging, and the fact that running a UPS near 100% shortens its life and eliminates redundancy. Standby generators are sized in kW with similar headroom, and for large GPU halls the step-load behavior matters — modern accelerators can swing hundreds of kW in milliseconds, which stresses generator governors and is a real topic to raise with your genset vendor.
Treat this as a first-pass estimate for feasibility and interconnection conversations. Actual one-line design — conductor sizing, fault current, selective coordination, transformer impedance — is stamped-engineer territory.