Amps to kW generator
Convert the load current to kW and kVA, then check how hard it works your generator and what size you need.
Inputs
Generator loading
How amps to kW generator calculator works
The amps to kW generator calculator converts load current into kilowatts (kW) and kilovolt-amperes (kVA) with 5 inputs: current, voltage, phase, power factor and generator rating. The calculator returns the generator load in percent and the next standard generator size above 125% of the load.
S = √3 × I × V / 1000 · P = S × 0.850 A at 400 V three phase is 34.64 kVA and 27.71 kW at PF 0.8, 87% of a 40 kVA generator. The suggested size is 45 kVA.
Amps to kW generator formula
The amps to kW generator formula is P(kW) = √3 × I × V × 0.8 / 1,000 for a three-phase generator at power factor 0.8. There are 3 generator formulas: apparent power, real power and generator size.
Apparent power (kVA)
S = √3 × I × V / 10001.732 × 50 A × 400 V / 1,000 = 34.64 kVA
Real power (kW)
P = S × PF34.64 kVA × 0.8 = 27.71 kW
Generator size
Size ≥ 1.25 × S1.25 × 34.64 kVA = 43.3 kVA → 45 kVA
Generators carry a kVA rating at power factor 0.8 under ISO 8528: the alternator heat limit depends on current and voltage, not on the load power factor. Keep the running load at or below 80% of the rating to leave headroom for motor starts.
Amps to kW generator conversion chart
The amps to kW generator conversion chart lists 15 generator sizes from 10 kVA to 500 kVA with the kW at power factor 0.8 and the full-load amps at 230 V single phase and 400 V and 480 V three phase.
| kVA | kWPF 0.8 | 230 V 1φamps | 400 V 3φamps | 480 V 3φamps |
|---|---|---|---|---|
| 10 kVA | 8 | 43.48 | 14.43 | 12.03 |
| 15 kVA | 12 | 65.22 | 21.65 | 18.04 |
| 20 kVA | 16 | 86.96 | 28.87 | 24.06 |
| 30 kVA | 24 | 130.43 | 43.3 | 36.08 |
| 45 kVA | 36 | 195.65 | 64.95 | 54.13 |
| 60 kVA | 48 | 260.87 | 86.6 | 72.17 |
| 80 kVA | 64 | 347.83 | 115.47 | 96.23 |
| 100 kVA | 80 | 434.78 | 144.34 | 120.28 |
| 125 kVA | 100 | 543.48 | 180.42 | 150.35 |
| 150 kVA | 120 | 652.17 | 216.51 | 180.42 |
| 200 kVA | 160 | 869.57 | 288.68 | 240.56 |
| 250 kVA | 200 | 1,086.96 | 360.84 | 300.7 |
| 300 kVA | 240 | 1,304.35 | 433.01 | 360.84 |
| 400 kVA | 320 | 1,739.13 | 577.35 | 481.13 |
| 500 kVA | 400 | 2,173.91 | 721.69 | 601.41 |
A 100 kVA generator delivers 80 kW and 144.3 A per phase at 400 V.
Amps to kW generator Excel formula
The amps to kW generator Excel formula is =SQRT(3)*A2*B2*C2/1000 with load amps in A2, volts in B2 and power factor 0.8 in C2.
| A | B | C | D | E | |
|---|---|---|---|---|---|
| 1 | Amps | Volts | PF | kW | Formula in D |
| 2 | 50 | 400 | 0.8 | 27.71 | =ROUND(SQRT(3)*A2*B2*C2/1000,2) |
| 3 | 120 | 480 | 0.8 | 79.81 | =ROUND(SQRT(3)*A3*B3*C3/1000,2) |
| 4 | 40 | 230 | 0.8 | 7.36 | =ROUND(A4*B4*C4/1000,2) |
Add =D2/C2*1.25 in column E to get the minimum generator size in kVA.
Amps to kW generator equation
The amps to kW generator equation is P = √3 × I × V × PF / 1,000, with PF = 0.8 for generator ratings.
- P
- Real power in kW
- I
- Load current in amperes (A)
- V
- Line-to-line voltage (V)
- 0.8
- Generator rating power factor
kW = kVA × 0.8 for every generator rated at PF 0.8: a 60 kVA generator gives 48 kW.
Amps to kW generator FAQ
How many kW is a 100 kVA generator?
A 100 kVA generator is 80 kW at a power factor of 0.8.
How many amps does a 60 kVA generator give at 400V?
A 60 kVA generator gives 86.6 A per phase at 400 V three phase and 72.2 A at 480 V.
What size generator for 50 amps 3 phase 400V?
50 amps 3 phase at 400V needs a 45 kVA generator: the load is 34.64 kVA, and 125% of the load is 43.3 kVA.
Why are generators rated in kVA?
Generators are rated in kVA as alternator heating depends on current and voltage, not on the load power factor. The rating assumes PF 0.8, so kW = kVA × 0.8.