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kVA and kW
Generator kVA to kW Explained
To convert generator kVA to kW, multiply by the power factor, which is typically 0.8 on three-phase generator ratings: 100 kVA × 0.8 = 80 kW, and 20 kVA × 0.8 = 16 kW. The data plate on your generator shows the power factor and kW for your set. To go the other way, divide kW by 0.8.
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- kW = kVA × power factor
- 0.8 is typical for generator ratings
- Your data plate has the final word
- Onsite across Gauteng
Apparent power and real power
Why are generators rated in kVA?
kVA is apparent power: the voltage and current the alternator can supply. kW is real power: the part your equipment turns into heat, light and motion. Power factor links the two. Generator makers typically rate three-phase sets at 0.8, so a 100 kVA set supplies 80 kW. Cummins, for example, rates its C330D5 at 330 kVA and 264 kW for standby use, which is exactly 0.8.
Your load has its own power factor. Heaters and kettles turn almost all of their kVA into kW. Motors, compressors and pumps draw extra current that does no useful work, so they need more kVA for the same kW. That is why we size a generator from both figures, not from a kW total alone.
Motor starting matters too. A motor draws far more current for a moment as it starts than when it runs, so a set can sit inside its kW rating and still dip or trip on start-up. Our generator size calculator adds the largest starting surge on top of your running load.
Worked examples
kVA to kW, step by step
Example 1: kVA to kW
Your plate reads 60 kVA at 0.8 power factor. 60 × 0.8 = 48 kW. That is the most real power the set delivers at its rating.
Example 2: kW to kVA
Your load adds up to 36 kW. 36 ÷ 0.8 = 45 kVA. With the 25% headroom our size calculator uses by default, you need about 56 kVA, so the next common size up is 60 kVA.
Example 3: per phase on a three-phase set
A 30 kVA three-phase set gives 30 × 0.8 = 24 kW, which is 8 kW per phase when the load is balanced. Put 12 kW of single-phase load on one phase and that phase overloads, even though the set carries only half its total rating.
Example 4: a real data plate
Cummins lists its C330D5 at 330 kVA / 264 kW standby and 300 kVA / 240 kW prime. Both pairs work out at 0.8. Use the pair that matches how you run the set.
kVA to kW conversion table at 0.8 power factor
kW = kVA × 0.8, the typical power factor for three-phase generator ratings. If your plate shows a different power factor, multiply by that figure instead.
| Generator kVA | kW at 0.8 power factor |
|---|---|
| 5 kVA | 4 kW |
| 10 kVA | 8 kW |
| 20 kVA | 16 kW |
| 30 kVA | 24 kW |
| 50 kVA | 40 kW |
| 60 kVA | 48 kW |
| 100 kVA | 80 kW |
| 150 kVA | 120 kW |
| 200 kVA | 160 kW |
| 250 kVA | 200 kW |
| 500 kVA | 400 kW |
| 750 kVA | 600 kW |
| 1 000 kVA | 800 kW |
Example 4 source: Cummins: C330D5 generator ratings. To size a generator from your appliances, including motor starting and headroom, use our generator size calculator.
Related Pages
Sizes, phase and the data plate
- Generator Size Calculator kVA from your appliances and motors
- Generator Sizes Common kVA bands
- Single-Phase vs Three-Phase How the supply is arranged
- Data Plate Guide Where kVA and kW are printed
- Load Bank Testing Prove output under a real load
- Fuel Consumption Litres per hour against the real load
- Generator Installation Sizing a new standby set
Common Questions
Questions about kVA and kW
How do I convert kVA to kW?
Multiply kVA by the power factor. Generator ratings typically use 0.8, so 100 kVA × 0.8 = 80 kW. Use the power factor on your data plate if it shows a different figure.
Is 100 kVA the same as 100 kW?
No. At the typical generator power factor of 0.8, 100 kVA gives 80 kW. To get 100 kW you need a 125 kVA set.
How do I convert kW to kVA?
Divide kW by the power factor. At 0.8, a 40 kW load needs 50 kVA before you add headroom for motor starting and future loads.
Why do generator plates show kVA?
Because the alternator’s limit is the voltage and current it can supply. The kW you can use depends on the power factor of your load.
Does every generator have a 0.8 power factor?
No. 0.8 is typical for three-phase generator ratings, but some plates show a different figure. Read the power factor on your data plate before you convert.
How do three-phase loads affect the rating?
A three-phase rating assumes the load is shared across three phases. A balanced 30 kVA set gives 8 kW per phase at 0.8, so 12 kW on one phase overloads it.
Can I size a generator from kW alone?
No. Power factor, phase balance and motor starting current all change what the set must supply. Our generator size calculator adds the starting surge and headroom for you.
Where do I find the real numbers for my set?
On the generator data plate: kVA, kW if printed, voltage and power factor. Our data plate guide walks through each field, and a photo of the plate is all we need to check it.
Still unsure what the fault is? Call or WhatsApp 082 057 4605 for onsite diagnosis.
Service Areas
Onsite visits across Gauteng
We come to your generator anywhere in Gauteng, 24/7. Choose your region for local suburbs, call-out details and the faults we see most there.
What to send before we attend
These details help us plan the visit and bring the right parts. Send what you can on WhatsApp; if you can’t find the model number, we still book the visit.
- Location
- The suburb or site, so the visit can be booked in the right area.
- Make and model
- The generator brand and model, if they are known.
- kVA
- The size printed on the data plate.
- Fuel type
- Diesel, petrol, LPG, natural gas, or dual-fuel.
- Controller model
- The module name on the panel, when it is visible.
- Fault or alarm
- What the set does, and any text on the screen.
- Photos
- The generator, the data plate, and the controller or alarm. Send these on WhatsApp.
Book a Visit
Send a photo of the rating plate
The kVA, kW and power factor on your plate tell us exactly what your set can deliver.
- Call
- 082 057 4605
- Message us on WhatsApp
What happens next
- We reply with questions about the generator, or to book a visit.
- A technician comes to you. For a breakdown we arrive within 1 hour.
- The fault is diagnosed on site and you get a written quote. No work starts until you accept it.
Charlie, lead technician: Degree in Mechanical Engineering, Degree in Electrical Engineering, Diesel Plant Fitter. Generator specialists since 2000.