Amps to kW converter
Converting amps to kW gives the real power, in kilowatts, that a current represents at a given voltage and power factor. It turns a service rating, a feeder size or a metered current into a figure comparable with equipment ratings, utility demand charges and generator outputs.
Convert amps to kW
Updates as the values change. The page address keeps the values for sharing.
The answer is the instantaneous power at that current. Energy, billed in kilowatt-hours, is that power multiplied by the hours it runs, so the converter is a starting point for estimates of demand and consumption rather than a measurement of either.
Formulas
DC
For a 48 V battery system delivering 100 A the power is 4.8 kW, the figure an inverter's continuous rating is compared with.
Single phase AC
On a 120/240 V service, the 240 V value applies to the service as a whole: a 200 A service carries up to 200 A on each leg, not 400 A in total.
Three phase AC
For a balanced three-phase feeder the current is the reading on any one line. An unbalanced load is converted phase by phase with the line-to-neutral voltage.
The result is real power. With the power factor set to 1 the same formulas give kVA, the apparent power the conductors and equipment carry.
Worked examples
The capacity of a 200 A, 120/240 V residential service
The service rating is entered as the current at 240 V, power factor 1.
P = V × I × PFP = 240 V × 200 A × 1 = 48,000 WP = 48,000 W ÷ 1,000 = 48 kW
The service corresponds to 48.0 kW at its full rating. The NEC sizes services from a load calculation under Article 220, in volt-amperes, rather than from this kind of capacity figure.
A 60 A feeder at 208 V three phase, PF 0.9
A subpanel feeder serving mixed lighting, receptacle and HVAC load.
P = √3 × V(L-L) × I × PFP = 1.732 × 208 V × 60 A × 0.9 = 19,454.4 WP = 19,454.4 W ÷ 1,000 = 19.454 kW
At full current the feeder delivers 19.45 kW of real power, or 21.62 kVA of apparent power.
35 A measured on a 480 V chiller, PF 0.85
A balanced three-phase compressor load measured with a clamp meter on one line.
P = √3 × V(L-L) × I × PFP = 1.732 × 480 V × 35 A × 0.85 = 24,733.7 WP = 24,733.7 W ÷ 1,000 = 24.734 kW
The chiller is drawing 24.73 kW. Running for ten hours at that load it would use about 247 kWh.
Conversion table
| Amps (A) | 120 V single phase (kW) | 240 V single phase (kW) | 208 V three phase (kW) | 480 V three phase (kW) |
|---|---|---|---|---|
| 5 | 0.60 | 1.20 | 1.80 | 4.16 |
| 10 | 1.20 | 2.40 | 3.60 | 8.31 |
| 15 | 1.80 | 3.60 | 5.40 | 12.47 |
| 20 | 2.40 | 4.80 | 7.21 | 16.63 |
| 30 | 3.60 | 7.20 | 10.81 | 24.94 |
| 40 | 4.80 | 9.60 | 14.41 | 33.26 |
| 50 | 6.00 | 12.00 | 18.01 | 41.57 |
| 60 | 7.20 | 14.40 | 21.62 | 49.88 |
| 70 | 8.40 | 16.80 | 25.22 | 58.20 |
| 80 | 9.60 | 19.20 | 28.82 | 66.51 |
| 100 | 12.00 | 24.00 | 36.03 | 83.14 |
| 125 | 15.00 | 30.00 | 45.03 | 103.92 |
| 150 | 18.00 | 36.00 | 54.04 | 124.71 |
| 200 | 24.00 | 48.00 | 72.05 | 166.28 |
| 225 | 27.00 | 54.00 | 81.06 | 187.06 |
| 400 | 48.00 | 96.00 | 144.11 | 332.55 |
Engine-generated values. At power factor 1 they equal kVA; for a load at PF 0.85, multiply a figure by 0.85 to get its real power.
Common mistakes
Adding both legs of a 120/240 V service
Multiplying a 200 A service by 120 V and then doubling for two legs gives the same 48 kW as 240 V × 200 A; adding 200 A on each leg as if 400 A flowed at 240 V doubles the true capacity.
Assuming the full rating can be used continuously
A breaker or service rating is not the load it should carry for hours. Continuous-load rules and the actual demand determine usable capacity; the converted figure is an upper bound.
Using 3 instead of √3 with 208 V or 480 V
With line-to-line voltage the factor is 1.732. Using 3 overstates three-phase power by about 73%, a common slip when the 3 × V(L-N) form of the formula is half remembered.
Confusing kW with kWh
Kilowatts are a rate; kilowatt-hours are energy. A 5 kW load running for 3 hours uses 15 kWh. A utility bill in kWh cannot be converted to amps without knowing how the load varied over time.
Frequently asked questions
How many kW is 200 amps?
At power factor 1, 200 A is 48.0 kW on a 240 V single-phase service and 72.1 kW on a 208 V three-phase service. At 480 V three phase it is 166.3 kW.
How many kW is 100 amps at 480 V three phase?
83.1 kW at power factor 1 and 74.8 kW at PF 0.9.
Is the result the power per phase or in total?
In total. The three-phase formula gives the power of all three phases together for a balanced load; the power on each phase is one third of it.
How does power factor change the answer?
Real power is apparent power times the power factor. At PF 0.8, 100 A at 240 V delivers 19.2 kW instead of 24 kW, though the conductors still carry the full 100 A.
Can amps be converted to kWh?
Only with a running time. kWh = kW × hours, so the current is converted to kW first and then multiplied by how long the load runs at that current.