How Many Amps Is 18 kW at 400V?

At 400V, 18 kW pulls approximately 30.57 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.

18 kW at 400V, AC three-phase (PF 0.85)

30.57 Amps

18 kilowatts at 400V on AC three-phase ≈ 30.57 amps

AC Single Phase (PF 0.85)52.94 A

DC (ideal baseline)45 A

Try: 20kW at 400V 15kW at 400V 22kW at 400V 12kW at 400V

Volts

Amps (AC three-phase, PF 0.85)

30.57

Formulas

DC: kW to Amps

I_(A) = 1000 × P_(kW) ÷ V_(V)

1000 × 18 ÷ 400 = 18,000 ÷ 400 = 45 A

AC Single Phase (PF = 0.85)

I_(A) = 1000 × P_(kW) ÷ (PF × V_(V))

18,000 ÷ (0.85 × 400) = 18,000 ÷ 340 = 52.94 A

AC Three Phase (PF = 0.85)

I_(A) = 1000 × P_(kW) ÷ (√3 × PF × V_L-L), where V_L-L is the line-to-line voltage

18,000 ÷ (1.732 × 0.85 × 400) = 18,000 ÷ 588.88 = 30.57 A

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 30.57A on AC three-phase at 400V, the load sits in the bracket between a 35A standard size (non-continuous) and the next size up that covers a continuous load under 210.19(A) (around 40A). 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

18 kW costs $3.06/hour at $0.17/kWh (rates last reviewed April 2026). See breakdown.

Power Factor Reference (AC three-phase)

How the line current for 18 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	18 kW at 400V (AC three-phase)
Resistive (heaters, incandescent)	1	25.98 A
Fluorescent lamps	0.95	27.35 A
LED lighting	0.9	28.87 A
Synchronous motors	0.9	28.87 A
Typical mixed loads	0.85	30.57 A
Induction motors (full load)	0.8	32.48 A
Computers (without PFC)	0.65	39.97 A
Induction motors (no load)	0.35	74.23 A

AC Conversion Comparison

On DC, 18kW at 400V draws 45A. AC single-phase at PF 0.85 pulls 52.94A because reactive current is added on top of the real power. Three-phase at the same voltage needs only 30.57A per line since the same 18kW is shared across three conductors instead of one.

Circuit Type	Formula	Result
DC	18,000 ÷ 400	45 A
AC Single Phase (PF 0.85)	18,000 ÷ (0.85 × 400)	52.94 A
AC Three Phase (PF 0.85)	18,000 ÷ (1.732 × 0.85 × 400)	30.57 A

Other kW Values at 400V

kW	AC 3-Phase per line, PF 0.85	AC 1-Phase PF 0.85
3 kW	5.09 A	8.82 A
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

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.

electrical_services 18 kW at 24V = 750A (DC) electrical_services 18 kW at 120V = 176.47A (1-phase) electrical_services 18 kW at 208V = 58.78A (3-phase) electrical_services 18 kW at 220V = 96.26A (1-phase) electrical_services 18 kW at 230V = 92.07A (1-phase) electrical_services 18 kW at 240V = 88.24A (1-phase) electrical_services 18 kW at 460V = 26.58A (3-phase) electrical_services 18 kW at 480V = 25.47A (3-phase) electrical_services 18 kW at 575V = 21.26A (3-phase)

Related Calculations

bolt 18,000W to amps at 400V payments 18,000W running cost cable Wire size for 30.57A at 400V (3Φ)

Frequently Asked Questions

How many amps is 18 kW at 400V?expand_more

18 kW at 400V draws about 30.57 amps on an AC three-phase circuit at PF 0.85. Alternate cases at the same voltage: 45A on DC, 52.94A on AC single-phase.

What size breaker would I need for 18 kW at 400V?expand_more

This is a sizing question, not a conversion question, and there is no single correct answer from a page like this. Breaker selection depends on the equipment nameplate FLA, whether the load is continuous (NEC 210.19(A) applies the 125% continuous-load rule), the conductor ampacity and temperature rating, any NEC 430/440 motor or HVAC provisions, and local code interpretation. Use the nameplate and a licensed electrician for the real install value; use this page only for the current-draw estimate that feeds into that process.

How much does 18 kW cost to run?expand_more

18 kW costs $3.06 per hour at $0.17/kWh (US residential average, last reviewed April 2026). At 8 hours/day that is $734.40 per month.

Why do industrial systems use kW instead of watts?expand_more

Industrial equipment operates at higher power levels. 18 kW is easier to express than 18,000W. The math is identical, just scaled by 1000.

How does three-phase affect the amps for 18 kW?expand_more

Three-phase at 400V draws 30.57A per line versus 52.94A single-phase. Less current per conductor means smaller wire and lower I²R losses.

This calculator provides estimates for reference purposes only. Always consult a licensed electrician and verify compliance with the National Electrical Code (NEC) and local electrical codes before performing any electrical work.