How Many Amps Is 4.2 kW at 208V?

At 208V, 4.2 kW pulls approximately 13.72 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.

4.2 kW at 208V, AC three-phase (PF 0.85)

13.72 Amps

4.2 kilowatts at 208V on AC three-phase ≈ 13.72 amps

AC Single Phase (PF 0.85)23.76 A

DC (ideal baseline)20.19 A

Try: 4kW at 208V 3.5kW at 208V 5kW at 208V 3kW at 208V

Volts

Amps (AC three-phase, PF 0.85)

13.72

Formulas

DC: kW to Amps

I_(A) = 1000 × P_(kW) ÷ V_(V)

1000 × 4.2 ÷ 208 = 4,200 ÷ 208 = 20.19 A

AC Single Phase (PF = 0.85)

I_(A) = 1000 × P_(kW) ÷ (PF × V_(V))

4,200 ÷ (0.85 × 208) = 4,200 ÷ 176.8 = 23.76 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

4,200 ÷ (1.732 × 0.85 × 208) = 4,200 ÷ 306.22 = 13.72 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 13.72A on AC three-phase at 208V, the load sits in the bracket between a 15A standard size (non-continuous) and the next size up that covers a continuous load under 210.19(A) (around 20A). 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

4.2 kW costs $0.71/hour at $0.17/kWh (rates last reviewed April 2026). See breakdown.

Power Factor Reference (AC three-phase)

How the line current for 4.2 kW at 208V 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	4.2 kW at 208V (AC three-phase)
Resistive (heaters, incandescent)	1	11.66 A
Fluorescent lamps	0.95	12.27 A
LED lighting	0.9	12.95 A
Synchronous motors	0.9	12.95 A
Typical mixed loads	0.85	13.72 A
Induction motors (full load)	0.8	14.57 A
Computers (without PFC)	0.65	17.94 A
Induction motors (no load)	0.35	33.31 A

AC Conversion Comparison

On DC, 4.2kW at 208V draws 20.19A. AC single-phase at PF 0.85 pulls 23.76A because reactive current is added on top of the real power. Three-phase at the same voltage needs only 13.72A per line since the same 4.2kW is shared across three conductors instead of one.

Circuit Type	Formula	Result
DC	4,200 ÷ 208	20.19 A
AC Single Phase (PF 0.85)	4,200 ÷ (0.85 × 208)	23.76 A
AC Three Phase (PF 0.85)	4,200 ÷ (1.732 × 0.85 × 208)	13.72 A

Other kW Values at 208V

kW	AC 3-Phase per line, PF 0.85	AC 1-Phase PF 0.85
0.5 kW	1.63 A	2.83 A
0.75 kW	2.45 A	4.24 A
1 kW	3.27 A	5.66 A
1.5 kW	4.9 A	8.48 A
2 kW	6.53 A	11.31 A
2.5 kW	8.16 A	14.14 A
3 kW	9.8 A	16.97 A
3.5 kW	11.43 A	19.8 A
4 kW	13.06 A	22.62 A
5 kW	16.33 A	28.28 A
6 kW	19.59 A	33.94 A
7.5 kW	24.49 A	42.42 A
8 kW	26.12 A	45.25 A
10 kW	32.66 A	56.56 A
12 kW	39.19 A	67.87 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.

Related Calculations

bolt 4,200W to amps at 208V payments 4,200W running cost cable Wire size for 13.72A at 208V (3Φ)

Frequently Asked Questions

How many amps is 4.2 kW at 208V?expand_more

4.2 kW at 208V draws about 13.72 amps on an AC three-phase circuit at PF 0.85. Alternate cases at the same voltage: 20.19A on DC, 23.76A on AC single-phase.

Why do industrial systems use kW instead of watts?expand_more

Industrial equipment operates at higher power levels. 4.2 kW is easier to express than 4,200W. The math is identical, just scaled by 1000.

How many amps does a 4.2 kW EV charger draw at 208V?expand_more

At 208V, a 4.2 kW EVSE draws about 23.76A on AC single-phase at PF 0.85. This is Level 2 territory, the standard residential (240V) or commercial (208V) AC charging tier covered by NEC Article 625. Home Level 2 units are typically 7.2 to 19.2 kW (30-80A); anything above that is usually commercial hardware or DC fast charging. Although the hero on this page shows the three-phase figure for 208V as the primary interpretation, real-world 208V commercial Level 2 EVSE is almost always wired single-phase across two wye legs, so the single-phase number above is the one a charger installer would use.

How does three-phase affect the amps for 4.2 kW?expand_more

Three-phase at 208V draws 13.72A per line versus 23.76A single-phase. Less current per conductor means smaller wire and lower I²R losses.

Is 4.2 kW single-phase or three-phase?expand_more

4.2 kW can be either. Residential loads up to about 5 kW (water heaters, dryers, EV chargers at 240V) are usually single-phase; commercial panels often serve the same load three-phase at 208V or 480V.

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.