How Many Amps Is 21.2 kW at 400V?
21.2 kW at 400V draws about 36 amps on an AC three-phase circuit at PF 0.85, typical for commercial HVAC, industrial motors, rooftop units, and three-phase panel loads. Actual current varies with equipment power factor and duty cycle.
Use this citation when referencing this page.
Formulas
DC: kW to Amps
I(A) = 1000 × P(kW) ÷ V(V)
AC Single Phase (PF = 0.85)
I(A) = 1000 × P(kW) ÷ (PF × V(V))
AC Three Phase (PF = 0.85)
I(A) = 1000 × P(kW) ÷ (√3 × PF × VL-L), where VL-L is the line-to-line voltage
Equipment & Circuit Sizing
Breaker Sizing
Breaker ratings are in amps, not watts, so the real install answer depends on the equipment nameplate FLA, whether the load is continuous (NEC 210.19(A) sizes the conductor and OCP at 125% of a continuous load, equivalently 80% of breaker rating), conductor ampacity and temperature rating, ambient and bundling derates, and any motor or HVAC provisions (NEC 430 / 440). At roughly 36A on AC three-phase at 400V, the load sits in the bracket between a 40A standard size (non-continuous) and the next size up that covers a continuous load under 210.19(A) (around 45A). The actual install pick depends on whether the load is continuous and the factors above; a conversion page can't pick a single "right" breaker from the amp draw alone.
Energy Cost
21.2 kW costs $3.60/hour at $0.17/kWh (rates last reviewed April 2026). See breakdown.
Power Factor Reference (AC three-phase)
How the line current for 21.2 kW at 400V changes with load power factor, on the same AC three-phase circuit basis the rest of the page uses. DC has no power factor; PF 1.0 represents resistive AC loads.
| Load Type | PF | 21.2 kW at 400V (AC three-phase) |
|---|---|---|
| Resistive (heaters, incandescent) | 1 | 30.6 A |
| Fluorescent lamps | 0.95 | 32.21 A |
| LED lighting | 0.9 | 34 A |
| Synchronous motors | 0.9 | 34 A |
| Typical mixed loads | 0.85 | 36 A |
| Induction motors (full load) | 0.8 | 38.25 A |
| Computers (without PFC) | 0.65 | 47.08 A |
| Induction motors (no load) | 0.35 | 87.43 A |
AC Conversion Comparison
On DC, 21.2kW at 400V draws 53A. AC single-phase at PF 0.85 pulls 62.35A because reactive current is added on top of the real power. Three-phase at the same voltage needs only 36A per line since the same 21.2kW is shared across three conductors instead of one.
| Circuit Type | Formula | Result |
|---|---|---|
| DC | 21,200 ÷ 400 | 53 A |
| AC Single Phase (PF 0.85) | 21,200 ÷ (0.85 × 400) | 62.35 A |
| AC Three Phase (PF 0.85) | 21,200 ÷ (1.732 × 0.85 × 400) | 36 A |
Other kW Values at 400V
| kW | AC 3-Phase per line, PF 0.85 | AC 1-Phase PF 0.85 |
|---|---|---|
| 3.5 kW | 5.94 A | 10.29 A |
| 4 kW | 6.79 A | 11.76 A |
| 5 kW | 8.49 A | 14.71 A |
| 6 kW | 10.19 A | 17.65 A |
| 7.5 kW | 12.74 A | 22.06 A |
| 8 kW | 13.58 A | 23.53 A |
| 10 kW | 16.98 A | 29.41 A |
| 12 kW | 20.38 A | 35.29 A |
| 15 kW | 25.47 A | 44.12 A |
| 18 kW | 30.57 A | 52.94 A |
| 20 kW | 33.96 A | 58.82 A |
| 22 kW | 37.36 A | 64.71 A |
| 25 kW | 42.45 A | 73.53 A |
| 30 kW | 50.94 A | 88.24 A |
| 35 kW | 59.43 A | 102.94 A |
Same kW, Other Voltages
Each destination page leads with the interpretation most common for that voltage, so the amps shown below use the same basis as the page you'd land on: single-phase for residential voltages, three-phase for commercial/industrial panel voltages, DC for low-voltage.