swap_horiz Looking to convert 18A at 240V back to watts?

How Many Amps Is 4,320 Watts at 240V?

4,320 watts equals 18 amps at 240V on an AC single-phase resistive circuit (PF 1.0). AC resistive at PF 1.0 and the DC baseline land on the same number at this voltage.

At 18A, the NEC 210.19(A) continuous-load sizing math (125% of the load, equivalently 80% of the breaker rating) points to a 25A breaker as the smallest standard size that covers this load continuously. A 20A breaker is the smallest standard size the raw current fits under, but it is non-continuous-only at this load. At 240V, the lower current draw allows smaller wire and breakers compared to 120V.

4,320 watts at 240V

18 Amps

4,320 watts equals 18 amps at 240 volts (AC single-phase, PF 1.0 resistive)

DC18 A

Try: 4,500W at 240V 4,000W at 240V 5,000W at 240V 3,500W at 240V

Watts

Volts

Amps (AC 1Φ, PF 1.0)

Assumes an AC single-phase resistive load at PF 1.0. Typing a commercial L-L voltage (208/400/480V) re-routes the result to three-phase; 277V stays on single-phase because it's the L-N lighting leg of a 480Y/277V wye; 12/24V re-routes to DC.

Formulas

DC: Watts to Amps

I_(A) = P_(W) ÷ V_(V)

4,320 ÷ 240 = 18 A

AC Single Phase (PF = 0.85)

I_(A) = P_(W) ÷ (PF × V_(V))

4,320 ÷ (0.85 × 240) = 4,320 ÷ 204 = 21.18 A

Circuit Sizing

Breaker Sizing

NEC 240.6(A) standard ampere ratings for branch-circuit and feeder breakers start at 15, 20, 25, 30, 35, 40, 45, and 50A and continue at 60A and above for feeder and large-appliance circuits. At 18A, the smallest standard breaker the raw current fits under is 20A, but that breaker only covers 20A non-continuously; NEC 210.19(A) requires conductor and OCP sized at 125% of any continuous load (equivalently 80% of breaker rating), so for a continuous load the smallest compliant breaker is 25A. Final selection still depends on the equipment nameplate, whether the load is continuous, conductor ampacity, and local code.

Breaker Size	Max Continuous Load (80%)	Status for 18A
15A	12A	Too small
20A	16A	Non-continuous only
25A	20A	OK for continuous
30A	24A	OK for continuous
35A	28A	OK for continuous
40A	32A	OK for continuous
45A	36A	OK for continuous
50A	40A	OK for continuous

Energy Cost

Running 4,320W costs approximately $0.73 per hour at the US average rate of $0.17/kWh (rates last reviewed April 2026). That is $5.88 for 8 hours or about $176.26 per month. See detailed cost breakdown.

AC Conversion Detail

The DC baseline for 4,320W at 240V is 18A. On an AC circuit with a power factor of 0.85, the current rises to 21.18A because reactive current flows alongside the real-power current.

Circuit Type	Formula	Result
DC	4,320 ÷ 240	18 A
AC Single Phase (PF 0.85)	4,320 ÷ (240 × 0.85)	21.18 A

Power Factor Reference

Power factor is the main reason 4,320W draws more current on AC than DC. At PF 1.0 (pure resistive, like a heater), the load pulls 18A at 240V on the single-phase basis the rest of the page uses. At PF 0.80 (typical induction motor), the same 4,320W pulls 22.5A. That is an extra 4.5A just to overcome the reactive component. Use the typical values below as a starting point, not for precise engineering calculations.

Load Type	Typical PF	4,320W at 240V (single-phase)
Resistive (heaters, incandescent)	1	18 A
Fluorescent lamps	0.95	18.95 A
LED lighting	0.9	20 A
Synchronous motors	0.9	20 A
Typical mixed loads	0.85	21.18 A
Induction motors (full load)	0.8	22.5 A
Computers (without PFC)	0.65	27.69 A
Induction motors (no load)	0.35	51.43 A

Same Wattage, Other Voltages

bolt4,320W at 12V = 360ADC bolt4,320W at 24V = 180ADC bolt4,320W at 100V = 43.2A1Φ, PF 1.0 bolt4,320W at 120V = 36A1Φ, PF 1.0 bolt4,320W at 208V = 14.11A3Φ per line, PF 0.85 bolt4,320W at 220V = 19.64A1Φ, PF 1.0 bolt4,320W at 230V = 18.78A1Φ, PF 1.0 bolt4,320W at 277V = 15.6A1Φ, PF 1.0 bolt4,320W at 400V = 7.34A3Φ per line, PF 0.85 bolt4,320W at 460V = 6.38A3Φ per line, PF 0.85 bolt4,320W at 480V = 6.11A3Φ per line, PF 0.85 bolt4,320W at 575V = 5.1A3Φ per line, PF 0.85

swap_horiz 18A to watts at 240V payments 4,320W running cost cable Wire size for 18A at 240V electrical_services 4.32 kW to amps science Ohm's law: 240V & 18A functions Watts to amps formula

Other Wattages at 240V

Watts	AC 1Φ Amps PF 1.0 resistive	AC 1Φ Amps PF 0.85 motor
1,200W	5A	5.88A
1,300W	5.42A	6.37A
1,400W	5.83A	6.86A
1,500W	6.25A	7.35A
1,600W	6.67A	7.84A
1,700W	7.08A	8.33A
1,800W	7.5A	8.82A
1,900W	7.92A	9.31A
2,000W	8.33A	9.8A
2,200W	9.17A	10.78A
2,400W	10A	11.76A
2,500W	10.42A	12.25A
2,700W	11.25A	13.24A
3,000W	12.5A	14.71A
3,500W	14.58A	17.16A
4,000W	16.67A	19.61A
4,500W	18.75A	22.06A
5,000W	20.83A	24.51A
6,000W	25A	29.41A
7,500W	31.25A	36.76A

Frequently Asked Questions

How many amps is 4,320W at 240V? expand_more

4,320W at 240V draws 18 amps on AC single-phase at PF 1.0 (resistive). For comparison at the same voltage: 18A on DC, 21.18A on AC single-phase at PF 0.85. Actual current depends on the load's power factor.

What kind of 240V outlet does a 4,320W appliance need? expand_more

At US 240V a "regular outlet" is not a standard 120V NEMA 5-15R household receptacle, it's a dedicated 240V branch-circuit receptacle sized to the load. At 4,320W on 240V the current is 18A, which typically maps to a NEMA 6-30 or 14-30 receptacle on a 240V/30A circuit (14-30 is the modern dryer outlet). Receptacle choice also depends on whether a neutral is needed, the equipment's cord and plug configuration, and any local amendments. Verify against the appliance's spec sheet and the receiving circuit.

What 240V circuit size does 4,320W need? expand_more

At 18A, a 240V/30A dedicated circuit is appropriate. The 24A continuous limit (30A × 0.8) covers sustained use, and 30A is also what most existing dryer circuits are wired for.

What is the 80% continuous load rule for 4,320W? expand_more

NEC 210.19(A) sizes the conductor and overcurrent device at not less than 125% of any continuous load (a load that runs three hours or more), equivalently 80% of the breaker rating. At 18A (the current the branch conductors actually carry on AC single-phase at PF 1.0 (resistive)), the minimum breaker that satisfies this is 25A under typical assumptions. Brief non-continuous use can run closer to the full breaker rating, but space heaters, EV chargers, and long-running appliances should be sized for the continuous case.

What power factor should I use for 4,320W calculations? expand_more

For resistive loads (heaters, incandescent bulbs, electric kettles) use PF 1.0. For motors, use 0.80. For mixed office/residential use 0.85. For computers and LED arrays the effective PF can be 0.65 or lower. Power factor only applies to AC.

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.