Real kilowatts are calculated—not read directly from a kVA plate. This guide shows how to calculate kW from kVA and power factor with worked examples for common PF values and load types.
Benefits
- Calculation: kW = kVA × PF (PF as decimal 0–1).
- Worked examples for PF 1.0, 0.9, and 0.8 motor-heavy sites.
- Sanity check: sum of load kW should not exceed calculated kW.
How it works
- Note apparent power in kVA from nameplate or electrical schedule.
- Select or measure power factor for the connected load mix.
- Multiply kVA × PF; record kW for fuel, battery, or capacity planning.
FAQ
How do I calculate kW from kVA and power factor?
kW = kVA × PF. Example: 30 kVA transformer at 0.88 PF → 30 × 0.88 = 26.4 kW real power capacity at that power factor. Repeat for each source if PF differs per bus.
What if I only know kW and need to check kVA?
Reverse the formula: kVA = kW ÷ PF. Example: 18 kW load at 0.75 PF draws 18 ÷ 0.75 = 24 kVA apparent—size breakers and conductors on 24 kVA, not 18.
Should I use nameplate kVA or running kVA?
Use operating kVA when you have meter data; use nameplate kVA for maximum equipment capability checks. Calculated kW from nameplate kVA × worst-case PF gives a conservative ceiling for what the gear can support.
Technical specifications
- kW = kVA × PF.
- kVA = kW ÷ PF (inverse).
- PF valid range in tool: 0 < PF ≤ 1.
- Related: convert-kva-to-kw-using-power-factor, inverter-sizing.