How Many Amps Is 31.8 kW at 400V?
At 400V, 31.8 kW pulls approximately 54 amps on AC three-phase (PF 0.85). This is the case typical for commercial HVAC, industrial motors, rooftop units, and three-phase panel loads. Always verify against the equipment nameplate for actual install sizing.
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 54A on AC three-phase at 400V, the load sits in the bracket between a 60A standard size (non-continuous) and the next size up that covers a continuous load under 210.19(A) (around 70A). 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
31.8 kW costs $5.41/hour at $0.17/kWh (rates last reviewed April 2026). See breakdown.
Power Factor Reference (AC three-phase)
How the line current for 31.8 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 | 31.8 kW at 400V (AC three-phase) |
|---|---|---|
| Resistive (heaters, incandescent) | 1 | 45.9 A |
| Fluorescent lamps | 0.95 | 48.32 A |
| LED lighting | 0.9 | 51 A |
| Synchronous motors | 0.9 | 51 A |
| Typical mixed loads | 0.85 | 54 A |
| Induction motors (full load) | 0.8 | 57.37 A |
| Computers (without PFC) | 0.65 | 70.61 A |
| Induction motors (no load) | 0.35 | 131.14 A |
AC Conversion Comparison
On DC, 31.8kW at 400V draws 79.5A. AC single-phase at PF 0.85 pulls 93.53A because reactive current is added on top of the real power. Three-phase at the same voltage needs only 54A per line since the same 31.8kW is shared across three conductors instead of one.
| Circuit Type | Formula | Result |
|---|---|---|
| DC | 31,800 ÷ 400 | 79.5 A |
| AC Single Phase (PF 0.85) | 31,800 ÷ (0.85 × 400) | 93.53 A |
| AC Three Phase (PF 0.85) | 31,800 ÷ (1.732 × 0.85 × 400) | 54 A |
Other kW Values at 400V
| kW | AC 3-Phase per line, PF 0.85 | AC 1-Phase PF 0.85 |
|---|---|---|
| 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 |
| 40 kW | 67.92 A | 117.65 A |
| 50 kW | 84.9 A | 147.06 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.