About

Sizing transformers and commercial generators requires a clear distinction between Real Power (kW) and Apparent Power (kVA). While kW measures the work actually performed, kVA accounts for the total capacity required by the system, including reactive power losses driven by inductive loads like motors and compressors. Engineers must often include a safety margin to prevent equipment overload during startup spikes. This tool integrates the Power Factor (PF) and an optional 20% buffer to recommend the next standard industrial transformer size, bridging the gap between calculation and procurement.

Formulas

The relationship between Apparent Power (S), Real Power (P), and Power Factor (PF) is:

SkVA = PkWPF

When the Safety Margin is applied (e.g., 20% or factor 1.2):

Srated = PkWPF × 1.20

Reference Data

Real Power (kW)	PF 1.0 (kVA)	PF 0.8 (kVA)	PF 0.6 (kVA)
10	10.0	12.5	16.7
50	50.0	62.5	83.3
100	100.0	125.0	166.7
250	250.0	312.5	416.7
500	500.0	625.0	833.3
800	800.0	1,000.0	1,333.3
1,000	1,000.0	1,250.0	1,666.7

Frequently Asked Questions

0.8 is the industry-standard estimate for mixed industrial loads involving induction motors. If you have purely resistive loads (like heaters), use a PF of 1.0. For heavy IT or welding loads, the PF might be lower.

Transformers should rarely run at 100% capacity continuously. A 20% margin allows for startup inrush currents, future expansion, and reduced thermal stress on the equipment.

Yes. The conversion from Total kW to Total kVA depends on Power Factor, not the phase count. However, sizing the specific amperage for cables would require knowing the phase count.

This is physically impossible. Real power (kW) is a component of Apparent power (kVA). kVA will always be equal to or greater than kW.