AmpSizerkW to amps
kW to amps
41.7 amps
from 10 kilowatts at 240 V, power factor 1.00
| Also equal to | Value |
|---|---|
| Current | 41.7 A |
| Real power | 10,000 W = 10.00 kW |
| Apparent power | 10,000 VA = 10.00 kVA |
| Mechanical equivalent | 13.41 HP |
| In milliamps | 41,667 mA |
- Breaker for this as a continuous load
- 60 A
- Copper conductor that carries it
- 6 AWG
This one does use the power factor. kW is real power, so getting to current means dividing it back out — 0.8 for a motor, 1 for a heater.
A sizing aid from the published NEC tables, not a design — have it signed off by a licensed electrician against the code your inspector enforces. Calculations follow the US NEC; outside the US, follow your local electrical code.
One circuit check a month
MonthlyOne thing a month worth measuring, testing or recalculating on a home electrical system — the part of sizing that happens after the install. No product pitches, and nothing that needs a live panel.
Try also
How do you convert kW to amps?
The AmpSizer kW-to-amps result for 10 kW on a 240 volt single-phase circuit at unity power factor is 41.7 amps. The formula is kW × 1,000 ÷ (volts × power factor), with 1.732 × volts for three phase.
Power factor belongs in this conversion and not in the kVA one. kW has already had the power factor taken out of it, so getting back to current means putting it back in — and the lower it is, the more current the same kilowatts demand.
At a power factor of 0.8, that same 10 kW needs 52.1 amps rather than 41.7. Sizing a conductor on the unity-power-factor figure for a motor load is a straightforward way to end up one size short.
The same kilowatts at the four voltages that cover almost all US work, at unity power factor.
| Load | 120 V, 1-ph | 240 V, 1-ph | 208 V, 3-ph | 480 V, 3-ph |
|---|---|---|---|---|
| 1 kW | 8.3 A | 4.2 A | 2.8 A | 1.2 A |
| 3 kW | 25.0 A | 12.5 A | 8.3 A | 3.6 A |
| 5 kW | 41.7 A | 20.8 A | 13.9 A | 6.0 A |
| 7.5 kW | 62.5 A | 31.3 A | 20.8 A | 9.0 A |
| 10 kW | 83.3 A | 41.7 A | 27.8 A | 12.0 A |
| 15 kW | 125.0 A | 62.5 A | 41.6 A | 18.0 A |
| 20 kW | 166.7 A | 83.3 A | 55.5 A | 24.1 A |
Multiply everything in the last two columns by 1.25 for a power factor of 0.8, which is the honest number for motor loads.
The kW, kVA and horsepower triangle
Three units, three conversions, and one of them has a trap in it:
- kW to kVA: divide by power factor. 10 kW at 0.8 is 12.5 kVA.
- kVA to amps: no power factor. 12.5 kVA at 240 V single phase is 52.1 A.
- kW to horsepower: divide by 0.7457, and remember it is output. 10 kW is 13.4 HP of shaft power.
Doing the first and the second in sequence gives the same current as doing kW to amps directly with the power factor in it. Doing kW to amps without the power factor and then applying it to the result is the one route that gives a wrong answer, and it is the common one.
Frequently asked questions
How many amps is 10 kW?
41.7 A at 240 V single phase, 12.0 A at 480 V three phase, and 27.8 A at 208 V three phase — all at unity power factor. At 0.8 power factor each of those rises by a quarter: 52.1, 15.0 and 34.7 A respectively.
Do I use kW or kVA to size the wire?
kVA, because the conductor carries current. Convert kW to kVA by dividing by the power factor, then kVA to amps. If you go straight from kW to amps you must include the power factor in that step — the two routes give the same answer, and skipping it in either gives one that is too low.
What is the difference between kW and kWh?
kW is a rate and kWh is a quantity. A 10 kW load running for three hours uses 30 kWh. Circuits are sized in kW because they care about the instant; bills are in kWh because they care about the month.
How do I convert kW to horsepower?
One mechanical horsepower is 0.7457 kW, so divide kW by 0.7457 — 10 kW is 13.4 HP. That is the shaft output equivalent. A motor rated 13.4 HP draws more than 10 kW of electrical input, by its efficiency, which for a mid-size motor is around 88 to 93%.
Why does the power factor make the wire bigger and not the breaker?
It makes both bigger, because both are sized from current. What it does not change is the energy on the bill, which stays at the kW figure. That asymmetry is exactly why utilities charge large customers for poor power factor: they carry the current and cannot sell it.
How we calculate this
kW × 1,000 ÷ (volts × power factor); three-phase is
kW × 1,000 ÷ (1.732 × volts × power factor) on the line-to-line voltage. Apparent power in kVA is
kW ÷ power factor. Horsepower conversion uses 745.7 watts per mechanical horsepower, which is shaft
output — a motor’s electrical input is higher by its efficiency, and neither the code tables nor this
conversion assume a value for that. Where a device and conductor are shown, the current is taken at 125%,
the device is the next standard rating in NEC 240.6(A), and the conductor satisfies Table 310.16 ampacity
with the small-conductor ceiling of 240.4(D) applied.Worked example
With Amount 10, Measured in kilowatts, Convert to amps, Voltage 240 V, Supply Single phase, Power factor 1.00, this page works out 41.7 amps. from 10 kilowatts at 240 V, power factor 1.00
- Breaker for this as a continuous load60 A
- Copper conductor that carries it6 AWG
Sources:
Which figure the nameplate gives you
Heating equipment gives kW and means it. A 9 kW tankless heater or a 5 kW duct heater is a resistive load at unity power factor, and kW to amps is a straight division.
Motors give horsepower or kW output. Neither is the input. The input is the output divided by the efficiency, and then the current comes from the input divided by the power factor.
Chargers and inverters give kW output too. An 11.5 kW charger delivers 11.5 kW to the car and draws a little more from the wall, but its rated input current is on the plate and that is the number to size on.