How Many Amps Does a 10 HP single-phase Motor Draw at 240V?

Q: What is 10 HP in watts?

10 HP equals 7,460 watts of mechanical output (1 HP = 746 W). The electrical input at the terminals is higher because no motor is 100% efficient: at 85% efficiency the input is about 8,776.47 W.

At 240V, 10 horsepower equals roughly 43.02 amps of running current on a single-phase circuit. One HP is 746 watts of mechanical output, but motors are not 100% efficient, so the electrical draw is higher. Applying V × Eff × PF: 7,460W ÷ (240 × 0.85 × 0.85) = 7,460 ÷ 173.4 = 43.02 A.

10 HP single-phase motor at 240V

43.02 Amps running

Calculated running current at the motor terminals at the assumed 85% efficiency and PF 0.85. This is a conversion from the nameplate horsepower using those assumptions, not a measured value; a real meter reading depends on the motor's actual nameplate efficiency, loading, temperature, and motor design.

NEC Table 430.248 FLC (code sizing base)50 A

Conductor min ampacity (NEC 430.22, 125% of FLC)62.5 A

Electrical input (HP × 746 ÷ efficiency)8,776.47 W

Try: 10HP at 240V 7.5HP at 240V 5HP at 240V 15HP at 240V

Volts

Motor Type

Running Amps (meter)

43.02

NEC Table 430.248 FLC (code sizing)

Use the running amps for metering and energy calculations. For branch-circuit sizing, AC motors use the NEC Table 430.248 / 430.250 full-load current under NEC 430.6(A)(1); DC motors use the motor nameplate full-load current under NEC 430.6(A)(3), with Table 430.247 as the reference. Three-phase current is shown per line on a balanced circuit.

Formula (single-phase)

I_(A) = (HP × 746) ÷ (V × Eff × PF)

(10 × 746) ÷ (240 × 0.85 × 0.85) = 7,460 ÷ 173.4 = 43.02 A

Convert HP to watts: 10 × 746 = 7,460W
Denominator: 240 × 0.85 × 0.85 = 173.4
Result: 7,460 ÷ 173.4 = 43.02 amps

NEC Reference Values

This section lists the Code reference numbers a motor branch circuit is sized from. Final conductor, breaker, disconnect, and overload selection is an install decision a licensed electrician makes against the motor nameplate, the actual install conditions, and the applicable NEC articles, not a decision a conversion page can make for you.

NEC Sizing Base: NEC Table 430.248 FLC

Per NEC 430.6(A)(1), motor branch-circuit conductors, switches, and overcurrent protection are sized from the values in Table 430.248 (single-phase) or Table 430.250 (three-phase), not from the motor nameplate and not from a calculated full-load amps. For a 10 HP single-phase motor at 240V, the table value is 50 A (the 115V column covers 110-120V systems under 430.6(A)(1)).

The 43.02 A shown in the hero is the calculated running current at 85% efficiency and PF 0.85. This is a conversion from the nameplate horsepower under those assumptions, not a measured value; a real meter reading depends on the motor's actual efficiency, loading, temperature, and design. Use this figure for energy and metering estimates, and use 50 A as the reference FLC when an electrician walks through NEC 430 against the nameplate.

NEC 430.22 Conductor Rule (reference formula)

NEC 430.22 requires motor branch-circuit conductor ampacity of at least 125% of the Code sizing FLC. As a reference calculation against the NEC Table 430.248 value: 50 × 1.25 = 62.5 A. The selected conductor is taken from NEC Table 310.16 at the applicable termination temperature column, with ambient, bundling, and cable-type adjustments applied by the installer. Motor branch-circuit conductors are exempt from the 240.4(D) small-conductor rule via 240.4(G).

NEC 430.52 Overcurrent Protection (code caps)

NEC Table 430.52(C)(1) gives the maximum rating for motor short-circuit and ground-fault protection as a percentage of the Code sizing FLC. The percentage depends on the device type:

Device Type	Maximum % of Table FLC (430.52(C)(1))
Non-time-delay fuse	300%
Dual-element (time-delay) fuse	175%
Inverse-time circuit breaker	250%
Instantaneous-trip circuit breaker	800%

These percentages are maximum caps, not install picks. A real circuit applies the percentage against the Code sizing FLC for the specific device type, rounds up to a standard size per 430.52(C)(1)(a), and is verified against the motor nameplate and the install conditions by the installer. The elevated percentages exist so short-circuit protection does not nuisance-trip on locked-rotor startup inrush.

Locked Rotor (Startup) Current

During the first 2-5 seconds of startup, a squirrel-cage induction motor typically draws 5 to 7 times the NEC Table 430.248 FLC of 50 A (roughly 250 to 350 A). This is why the 430.52(C)(1) percentages above are so much higher than running current: the short-circuit/ground-fault protective device has to ride through locked-rotor inrush without tripping. Actual LRA is set by the motor's NEMA code letter on the nameplate and should be checked there for a real install.

Current	Amps	Duration
Calculated running current (meter)	43.02 A	Continuous at full load
NEC Table 430.248 FLC (Code reference)	50 A	Sizing base, not metered
Locked rotor (typical, 5-7×)	250-350 A	2-5 seconds

Operating Cost

Motor mechanical output is 7,460 W (10 HP × 746). Electrical input at the terminals is higher because no motor is 100% efficient: 7,460 ÷ 0.85 = 8,776.47 W. At $0.17/kWh, running cost is $1.49/hour or $358.08/month at 8 hours/day. Full breakdown at 8,776.47 W.

Amps by Motor Efficiency (single-phase)

Motor efficiency directly affects amp draw. A more efficient motor draws less current for the same HP output. Values below are the calculated single-phase running current at 240V and PF 0.85:

Efficiency	Amps at 240V	Watts Consumed	Waste Heat
75%	48.76 A	9,946.67 W	2,486.67 W
80%	45.71 A	9,325 W	1,865 W
85%	43.02 A	8,776.47 W	1,316.47 W
90%	40.63 A	8,288.89 W	828.89 W
95%	38.49 A	7,852.63 W	392.63 W

Other HP Values at 240V (single-phase)

Running current is the calculated single-phase draw at 85% efficiency and 0.85 PF (a conversion from HP under those assumptions, not a measured value). NEC Table FLC is the value from NEC Table 430.248 used for branch-circuit conductor and OCP sizing under NEC 430.6(A)(1). LRA is estimated at 5-7× the NEC table FLC; rows outside the table show n/a because there is no code-authoritative LRA basis for that HP/voltage/phase combination. Row links open each result page in single-phase mode.

HP	Running Amps (calculated)	NEC Table 430.248 FLC	LRA Estimate (5-7× FLC)
1/8 HP	0.5378 A	off-table	n/a
1/6 HP	0.7172 A	2.2 A	11-15.4 A
1/4 HP	1.08 A	2.9 A	14.5-20.3 A
1/3 HP	1.43 A	3.6 A	18-25.2 A
1/2 HP	2.15 A	4.9 A	24.5-34.3 A
3/4 HP	3.23 A	6.9 A	34.5-48.3 A
1 HP	4.3 A	8 A	40-56 A
1.5 HP	6.45 A	10 A	50-70 A
2 HP	8.6 A	12 A	60-84 A
3 HP	12.91 A	17 A	85-119 A
5 HP	21.51 A	28 A	140-196 A
7.5 HP	32.27 A	40 A	200-280 A
10 HP	43.02 A	50 A	250-350 A
15 HP	64.53 A	off-table	n/a
20 HP	86.04 A	off-table	n/a
25 HP	107.55 A	off-table	n/a
30 HP	129.07 A	off-table	n/a
40 HP	172.09 A	off-table	n/a
50 HP	215.11 A	off-table	n/a
75 HP	322.66 A	off-table	n/a

Same HP, Other Voltages (single-phase)

speed 10 HP at 120V = 86.04A speed 10 HP at 208V = 49.64A speed 10 HP at 220V = 46.93A speed 10 HP at 230V = 44.89A speed 10 HP at 400V = 25.81A speed 10 HP at 480V = 21.51A

Related Calculations

bolt 8,776W electrical input to amps at 240V payments 8,776W running cost cable Wire size for 62.5A at 240V (NEC 430.22 minimum: 125% of 50A NEC Table 430.248 FLC)

Frequently Asked Questions

How many amps does a 10 HP single-phase motor draw at 240V?expand_more

At the terminals, a 10 HP single-phase motor at 240V draws about 43.02 amps at 85% efficiency and 0.85 power factor. For NEC branch-circuit sizing use the NEC Table 430.248 full-load current instead: 50 A.

What is 10 HP in watts?expand_more

10 HP equals 7,460 watts of mechanical output (1 HP = 746 W). The electrical input at the terminals is higher because no motor is 100% efficient: at 85% efficiency the input is about 8,776.47 W.

What does NEC 430.52(C)(1) say about OCP for a 10 HP single-phase motor?expand_more

NEC Table 430.52(C)(1) gives the maximum OCP rating as a percentage of the NEC Table 430.248 FLC. The ceilings by device type are 300% for non-time-delay fuses, 175% for dual-element (time-delay) fuses, 250% for inverse-time circuit breakers, and 800% for instantaneous-trip breakers. These percentages are ceilings, not starting points, and 250% is not a blanket motor rule. The actual max for a specific install comes from picking the device type, applying the matching percentage to the 50 A NEC Table 430.248 FLC, rounding up to a standard size per 430.52(C)(1)(a), and verifying against the motor startup profile.

What branch-circuit context does a 10 HP single-phase motor at 240V typically sit in?expand_more

At 240V single-phase, motor branches are dedicated circuits, not general-purpose receptacles. Common NEMA configurations at this voltage are the 6-series (6-15, 6-20, 6-30, 6-50) and the 14-series (14-30, 14-50) when a neutral is needed, sized to the motor branch-circuit OCP the installer picks under NEC 430.52(C)(1). The NEC Table 430.248 FLC of 50 A is the reference number an electrician feeds into 430.22 and 430.52, not a receptacle pick on its own. Verify against the nameplate and local code.

Does motor efficiency affect amp draw?expand_more

Yes. A 10 HP single-phase motor at 90% efficiency draws 40.63 A at the terminals versus 48.76 A at 75% efficiency. Higher efficiency means lower running amps and lower electrical input wattage for the same mechanical output.

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.