Quick answer: To convert kVA to kW, multiply the apparent power in kVA by the power factor: kW = kVA × pf. At a power factor of 0.8, a 100 kVA supply gives 80 kW. To go the other way, divide: kVA = kW ÷ pf. If you do not know the power factor, use 0.8 for motor and mixed loads, and 1.0 for purely resistive loads such as heaters.
What kVA and kW actually mean
kVA and kW both measure electrical power, but they are not the same thing. The difference is the reason your generator is rated in one unit and your load schedule is written in the other.
- kVA (kilovolt-amperes) is apparent power — the total power the supply has to deliver. It is simply voltage multiplied by current, so it includes everything the cable and the source must carry.
- kW (kilowatts) is real power — the part that does useful things: turning a motor shaft, producing heat, giving light. This is what your electricity meter bills and what the load actually consumes.
- kVAR (kilovolt-amperes reactive) is reactive power — the part that flows back and forth to build the magnetic fields inside motors and transformers. It does no useful output but still loads the cable and the generator.
These three form the power triangle. Apparent power (kVA) is the longest side, real power (kW) and reactive power (kVAR) are the other two sides, and the angle between kVA and kW is the phase angle. The cosine of that angle is the power factor.
The kVA to kW formula
kW = kVA × pf
kVA = kW ÷ pf
kVAR = √(kVA² − kW²)
pf = kW ÷ kVA (this is cos θ, the power factor)Power factor is a number between 0 and 1. A power factor of 1 means every volt-ampere delivered turns into real power, so kVA and kW are equal. As the power factor falls, more of the supply is tied up in reactive power and the gap between kVA and kW widens.
Notice that the conversion does not depend on voltage or on whether the system is single-phase or three-phase. Voltage and phase only matter when you also want the current, which is covered further down.
Enter kVA, power factor and voltage — get kW, kVAR and full-load current for single or three-phase systems.
Open the kVA to kW Calculator →Why is power factor the whole story?
Power factor tells you how much of the apparent power is doing real work. It is set by the type of load, not by you:
| Load type | Typical power factor |
|---|---|
| Electric heater, incandescent lamp, oven | 1.0 |
| LED and electronic lighting | 0.9 – 0.95 |
| Induction motor at full load | 0.82 – 0.87 |
| Induction motor at part load | 0.5 – 0.7 |
| Welding set | 0.4 – 0.6 |
| Mixed commercial building | 0.85 – 0.9 |
This is why a data sheet that only gives kVA is not enough on its own. A 500 kVA transformer feeding a heater bank delivers close to 500 kW, but the same transformer feeding lightly loaded motors at 0.6 power factor delivers only about 300 kW of useful output.
kVA to kW conversion chart (power factor 0.8)
Most standby generators and many load schedules assume a power factor of 0.8, so this is the chart people reach for most often.
| kVA | kW at pf 0.8 | kVAR |
|---|---|---|
| 1 | 0.8 | 0.6 |
| 5 | 4 | 3 |
| 10 | 8 | 6 |
| 15 | 12 | 9 |
| 20 | 16 | 12 |
| 25 | 20 | 15 |
| 30 | 24 | 18 |
| 40 | 32 | 24 |
| 50 | 40 | 30 |
| 62.5 | 50 | 37.5 |
| 100 | 80 | 60 |
| 125 | 100 | 75 |
| 160 | 128 | 96 |
| 200 | 160 | 120 |
| 250 | 200 | 150 |
| 500 | 400 | 300 |
| 1000 | 800 | 600 |
kVA to kW at other power factors
Change the power factor and the kW value moves with it. The chart below shows how much real power the same kVA delivers as the power factor changes.
| kVA | pf 1.0 | pf 0.9 | pf 0.8 | pf 0.7 |
|---|---|---|---|---|
| 10 | 10 kW | 9 kW | 8 kW | 7 kW |
| 25 | 25 kW | 22.5 kW | 20 kW | 17.5 kW |
| 50 | 50 kW | 45 kW | 40 kW | 35 kW |
| 100 | 100 kW | 90 kW | 80 kW | 70 kW |
| 250 | 250 kW | 225 kW | 200 kW | 175 kW |
Example — a 100 kVA generator
A standby generator is stamped 100 kVA, 415 V, three-phase, 0.8 power factor. You want to know how much real load it can carry and how much current it delivers.
- Real power: kW = 100 × 0.8 = 80 kW
- Reactive power: kVAR = √(100² − 80²) = √3600 = 60 kVAR
- Full-load current: I = (100 × 1000) ÷ (√3 × 415) = 139 A
So the set can supply 80 kW of useful load. If your load list adds up to 90 kW, this generator is undersized even though "100" looks bigger than "90" — because the 100 is kVA and the 90 is kW.
Single-phase and three-phase — does it change the conversion?
No. The kVA to kW conversion is kW = kVA × pf whether the supply is single-phase or three-phase. The number of phases only changes how you calculate current from that power, not the relationship between apparent and real power.
People often mix this up because the current formulas look different. For the same kVA, a three-phase supply draws less current per conductor than a single-phase supply at the same voltage, which is one of the reasons larger loads are three-phase. But the split between kVA and kW is identical. If a data sheet gives you kVA and power factor, you can find kW without ever knowing how many phases are involved.
kVA, kW and horsepower
Motors are often listed in horsepower, so it helps to see how the three units line up. One metric horsepower is 0.736 kW, and one mechanical (imperial) horsepower is 0.746 kW. That figure is the output at the shaft. The electrical input is larger, because the motor is not 100% efficient, and the input kVA is larger still, because of the power factor.
Shaft output (kW) = HP × 0.746
Electrical input (kW) = shaft output ÷ efficiency
Input kVA = input kW ÷ power factor| Motor | Shaft kW | Input kW (90% eff.) | Input kVA (0.85 pf) |
|---|---|---|---|
| 5 HP | 3.7 | 4.1 | 4.9 |
| 10 HP | 7.5 | 8.3 | 9.8 |
| 25 HP | 18.6 | 20.7 | 24.4 |
| 50 HP | 37.3 | 41.4 | 48.7 |
| 100 HP | 74.6 | 82.9 | 97.5 |
This is why a 100 HP motor lands close to 100 kVA of demand — the horsepower, the inefficiency and the power factor stack up. To size the supply cable to a motor from its full-load current, use the motor full-load current calculator.
Finding the current from kVA
Once you have kVA and the system voltage, the line current follows directly. Current does not need the power factor because kVA already includes it.
Three-phase: I = (kVA × 1000) ÷ (√3 × V) (V = line-to-line voltage)
Single-phase: I = (kVA × 1000) ÷ V| kVA | Current at 415 V, 3-phase | Current at 230 V, 1-phase |
|---|---|---|
| 5 | 7.0 A | 21.7 A |
| 10 | 13.9 A | 43.5 A |
| 25 | 34.8 A | 108.7 A |
| 50 | 69.6 A | 217.4 A |
| 100 | 139.1 A | — |
These currents feed straight into cable and breaker selection. Once you know the full-load current, size the feeder with the cable size calculator and confirm the run length with the voltage drop calculator.
Why generators and transformers are rated in kVA
A generator or transformer is limited by heat, and heat comes from current, not from useful output. Current is set by kVA, because the winding and the cable have to carry the reactive part as well as the real part. The manufacturer has no idea what power factor your load will run at, so rating the machine in kVA keeps the rating honest for any load.
The moment a power factor is quoted, real power becomes fixed. A genset marked "100 kVA / 80 kW at 0.8 pf" is telling you both numbers: the 100 kVA is the thermal limit of the alternator, and 80 kW is what you get if you load it at 0.8 power factor. Run it at 0.9 power factor and it can give 90 kW before the alternator reaches the same 100 kVA limit — but check the engine, because the engine is often the real cap on kW.
Converting kW back to kVA
Sizing often runs the other way: you have a real load in kW and need the kVA so you can pick a transformer or generator. Divide by the power factor.
kVA = kW ÷ pfA building with a 160 kW connected load at 0.85 power factor needs kVA = 160 ÷ 0.85 = 188 kVA, so a 200 kVA transformer is the sensible next standard size. If you improve the power factor to 0.95 with capacitors, the same 160 kW needs only 168 kVA — which is how power factor correction frees up spare capacity without adding a bigger transformer.
Power factor correction — a worked saving
Because kVA = kW ÷ pf, raising the power factor shrinks the kVA the source has to carry for the same real load. That is the whole point of power factor correction: fit capacitors that supply the reactive power locally, so the supply only has to carry the real part.
Take a factory drawing 160 kW at a poor power factor of 0.75. The apparent power is 160 ÷ 0.75 = 213 kVA. Improve the power factor to 0.95 with a capacitor bank and the apparent power falls to 160 ÷ 0.95 = 168 kVA — a drop of 45 kVA. The capacitor size needed is the difference in reactive power:
kVAR before = √(213² − 160²) = 141 kVAR
kVAR after = √(168² − 160²) = 51 kVAR
Capacitor size = 141 − 51 = 90 kVARA 90 kVAR bank frees 45 kVA of supply capacity, reduces cable current, and often removes a utility penalty for low power factor. The reactive side of this is covered in power factor correction with capacitors, and the bank can be sized with the power factor correction calculator.
Sizing a transformer from a kW load
Transformers are ordered in kVA, but your load list is in kW. Convert the total kW to kVA at the expected power factor, then step up to the next standard transformer size, leaving room for growth.
| Building load | Power factor | Required kVA | Standard transformer |
|---|---|---|---|
| 80 kW | 0.9 | 89 kVA | 100 kVA |
| 160 kW | 0.85 | 188 kVA | 200 kVA |
| 300 kW | 0.9 | 333 kVA | 400 kVA |
| 800 kW | 0.9 | 889 kVA | 1000 kVA |
Standard distribution transformers come in fixed ratings — 100, 160, 200, 250, 315, 400, 500, 630, 1000 kVA — so always round up. Full transformer sizing to a standard, including diversity and future load, is set out in the transformer sizing calculator.
Reading an electrical nameplate
Nameplates mix these units, and reading them correctly avoids sizing errors:
- Motors are stamped in kW or HP of shaft output, plus a full-load current and power factor. The input kVA is larger than the kW because of efficiency and power factor.
- Generators are stamped in kVA and kW, with the rated power factor (usually 0.8). The kVA is the alternator limit; the kW is the engine limit.
- Transformers are stamped in kVA only, with no power factor, because the transformer does not know the load it will feed.
- UPS units are stamped in both kVA and kW; modern units are close to 1.0 power factor, so the two numbers are nearly equal.
Common mistakes to avoid
- Treating kVA and kW as interchangeable. They are only equal at a power factor of 1, which almost never happens with motors.
- Assuming 0.8 power factor everywhere. Modern LED and electronic loads run closer to 0.9–0.95. Using 0.8 by habit undersizes the real power you can draw.
- Comparing a kW load to a kVA rating. Always convert both to the same unit before you decide if the source is big enough.
- Forgetting the engine limit on a genset. The alternator is kVA-limited, but the diesel engine behind it is kW-limited. The set can never exceed either.
Key points to remember
- kW = kVA × power factor; kVA = kW ÷ power factor.
- kVA is what the supply carries; kW is what the load uses; the gap is reactive power.
- Power factor is fixed by the load type — 0.8 for motors, 1.0 for heaters, 0.9+ for electronic loads.
- Generators and transformers are rated in kVA because their limit is current, not useful output.
- Improving power factor with capacitors lets the same source deliver more kW.
For the reactive side of the same triangle, see power factor correction with capacitors, and for source sizing read how to size a generator in kVA.
Frequently asked questions
How many kW is 1 kVA?
At a power factor of 0.8, 1 kVA equals 0.8 kW. At unity power factor 1 kVA equals 1 kW. Multiply the kVA by the power factor to get kW.
What is the formula to convert kVA to kW?
kW = kVA multiplied by the power factor. To go the other way, kVA = kW divided by the power factor.
Is kVA bigger than kW?
Yes, unless the power factor is exactly 1. kVA is apparent power and is always equal to or greater than kW; the difference is the reactive power (kVAR).
How many kW is a 100 kVA generator?
About 80 kW at a power factor of 0.8, or 90 kW at 0.9. The generator nameplate states the power factor it is rated at.
Why are generators rated in kVA and not kW?
Because a generator is limited by heat, which comes from current. Current is set by kVA regardless of the load power factor, so a kVA rating stays valid for any load.