How Many Amps Is 250 kVA at 480V?

A 250 kVA three-phase load at 480V pulls 300.7 amps per line. The same apparent power on a single-phase circuit at 480V would carry 520.83 amps in a single conductor. Three-phase spreads the apparent power across three lines, so each conductor and breaker can be smaller for the same apparent-power figure.

250 kVA equals 300.7 amps at 480 volts (three-phase, L-L)

300.7 Amps

Single Phase (480V)520.83 A

Try: 200kVA at 480V 150kVA at 480V 100kVA at 480V 75kVA at 480V

kVA

Volts

Amps (3Φ per line)

300.7

Assumes an AC three-phase line-to-line circuit at the input voltage. kVA is apparent power, so no power factor term is involved.

Formulas

Single Phase

I_(A) = (kVA × 1000) ÷ V

(250 × 1000) ÷ 480 = 250,000 ÷ 480 = 520.83 A

Three Phase (480V Line-to-Line)

I_(A) = (kVA × 1000) ÷ (V_L-L × √3)

250,000 ÷ (480 × 1.732) = 250,000 ÷ 831.36 = 300.7 A

Applies to 480Y/277 or 480 delta systems where 480V is the line-to-line voltage.

Single Phase vs Three Phase

The same 250 kVA unit draws very different current depending on the phase configuration:

Configuration	Formula	Current at 480V
Single Phase	250,000 ÷ 480	520.83 A
Three Phase (480V L-L)	250,000 ÷ (480 × √3)	300.7 A

For this specific case, 250 kVA at 480V, three-phase carries about 42.26% less current per line than single-phase at the same voltage. That gap tracks the 1 ÷ √3 factor for L-L three-phase (or 1 ÷ 3 for L-N), which is why three-phase distribution is common at commercial and industrial scale: the same apparent power rides on smaller conductors and smaller breakers (applies to 480Y/277 or 480 delta systems).

Generator & UPS Sizing

Load-Side Real Power by Power Factor

A load with an apparent power of 250 kVA draws different amounts of real power depending on the load's own power factor. The table below is a load-side conversion, not a forecast of what a generator or UPS will output for that load: generators and UPS units publish their own independent kW rating set by the engine or inverter design, and that rating is often lower than kVA × the load's PF.

Load Type	Load PF	Load Real Power (kW)	Current at 480V (three-phase, per line)
Resistive (heaters, lights)	1.0	250 kW	300.7 A per line
Mixed typical	0.85	212.5 kW	300.7 A per line
Motors/HVAC	0.80	200 kW	300.7 A per line
Computers/servers (no PFC)	0.65	162.5 kW	300.7 A per line

Note: current draw stays the same across the rows because kVA sets the current, not the load's power factor. PF only affects how much real work (kW) the load does per amp drawn.

Sizing a load against a source. If you are feeding this load from a UPS, generator, or transformer, check the load against both the source's kVA rating AND the source's kW rating. Those are two independent numbers published by the manufacturer. A 10 kVA / 8 kW generator, for example, can supply up to 10 kVA of apparent power AND up to 8 kW of real power, whichever limit is reached first. Do not use the kW figures above as a substitute for the source's published kW rating.

Circuit Sizing: Starting Points

The numbers below are rough order-of-magnitude starting points under typical assumptions (copper conductors, 75°C terminations, short run, no ambient or bundling derates, non-continuous duty). They are not install specs. Actual breaker and wire selection depends on the equipment nameplate, conductor and termination temperature ratings, cable type, run length and voltage-drop target, ambient and bundling conditions, whether the load is continuous, any NEC 430/440 motor or HVAC provisions, and local code.

	Single Phase	Three Phase
Current draw (at full kVA)	520.83 A	300.7 A
Ballpark branch OCP	~600A	~350A

For a real install, run the full wire-size calculator with your actual run length, voltage, and drop target, and verify breaker selection against the equipment nameplate and local code.

Energy Cost at Full Load

A load with an apparent power of 250 kVA at load PF 0.85 draws 212.5 kW of real power. Running cost at that draw: $36.13/hour at $0.17/kWh (rates last reviewed April 2026), or $8,670.00/month (8h/day). Full breakdown.

kW Equivalent

250 kVA at PF 0.85 = 212.5 kW. See 212.5 kW to amps at 480V.

Other kVA Ratings at 480V

kVA	Three Phase Amps (L-L, per line)	Single Phase Amps	Real Power (PF 0.8)
10 kVA	12.03 A	20.83 A	8 kW
15 kVA	18.04 A	31.25 A	12 kW
20 kVA	24.06 A	41.67 A	16 kW
25 kVA	30.07 A	52.08 A	20 kW
30 kVA	36.08 A	62.5 A	24 kW
40 kVA	48.11 A	83.33 A	32 kW
50 kVA	60.14 A	104.17 A	40 kW
75 kVA	90.21 A	156.25 A	60 kW
100 kVA	120.28 A	208.33 A	80 kW
150 kVA	180.42 A	312.5 A	120 kW
200 kVA	240.56 A	416.67 A	160 kW
250 kVA	300.7 A	520.83 A	200 kW

Frequently Asked Questions

How many amps is 250 kVA at 480V?expand_more

250 kVA at 480V is 300.7 amps per line on a three-phase circuit (480Y/277 or 480 delta), or 520.83 amps on single-phase at the same voltage.

What is the difference between kVA and kW?expand_more

kVA is apparent power (V×I), which sets the current on the circuit and the sizing of conductors, breakers, and windings. kW is real power (the portion that does useful work), equal to kVA×load PF. A load with an apparent power of 250 kVA at load PF 0.8 draws 200 kW of real power. For a source such as a generator or UPS, kVA and kW are two independent manufacturer ratings, not two views of the same spec, and both have to be checked when sizing a load.

What size generator do I need for my loads?expand_more

Generator sizing is not a single-formula calculation. A rough napkin pass is: add up the steady-state watts of everything you plan to run, divide by a planning power factor (often 0.8 but not universal), and add margin. Then cross-check the result against the generator's published kW rating, which is a separate manufacturer spec set by the engine (prime mover) and is not derived from the generator's kVA rating by any formula. The caveats that matter for a real install: motor and compressor inrush can be several times steady-state current, load diversity and sequencing affect peak demand, voltage-dip tolerance of sensitive equipment limits how much motor load a given genset can start, and altitude and ambient temperature both derate output. A load with an apparent power of 250 kVA at PF 0.8 has a real-power draw of 200 kW, but that number alone is not sufficient to size a generator for a real installation.

Can a 250 kVA generator run my whole house?expand_more

A 250 kVA unit can typically handle a full house including central AC, provided simultaneous motor starting is managed and the actual connected load fits. An electrician should run an NEC 220 load calc against your specific panel before committing to a size.

Three-phase vs single-phase for 250 kVA?expand_more

Three-phase (480Y/277 or 480 delta) draws 300.7A per line. Single-phase at the same voltage draws 520.83A. Three-phase delivers the same apparent power across three conductors, so each line carries less current and the wire and breakers can be smaller for the same kVA.

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.