When comparing diesel generators, you will often see two power ratings: kW and kVA. Understanding the difference helps you compare quotations and choose equipment that matches your electrical load.
kW measures real power, while kVA measures apparent power. The relationship between them depends on the power factor. For example, 100 kVA corresponds to 80 kW at a power factor of 0.8.
What Is kW?
kW stands for kilowatt. It measures the real electrical power used to perform work, such as running machinery, producing heat or powering lighting.
A generator’s electrical kW rating tells you the real power it can supply under its specified operating conditions. It should not be confused with the diesel engine’s mechanical power rating.
What Is kVA?
kVA stands for kilovolt-ampere. It measures apparent power, which depends on voltage and current. It accounts for the electrical demand associated with both real and reactive power.
This matters because an alternator must carry the current required by the load, even when some of that current does not contribute to real power.
| Measurement | kW | kVA |
|---|---|---|
| Full name | Kilowatt | Kilovolt-ampere |
| Power measured | Real power | Apparent power |
| Main sizing check | Real power required by the equipment | Voltage and current demand on the alternator |
How to Convert kVA to kW
Use these formulas:
kW = kVA × Power Factor
kVA = kW ÷ Power Factor
Many industrial three-phase diesel generators are rated at 0.8 lagging power factor. Use that value only when it matches the rating or load you are calculating.
The following examples assume a power factor of 0.8:
| kVA | Equivalent kW at PF 0.8 |
|---|---|
| 30 kVA | 24 kW |
| 60 kVA | 48 kW |
| 100 kVA | 80 kW |
| 125 kVA | 100 kW |
| 250 kVA | 200 kW |
| 500 kVA | 400 kW |
These are mathematical conversions, not a substitute for checking a particular generator’s datasheet.
Is Power Factor Always 0.8?
No. The operating power factor depends on the connected load. The generator’s stated rating power factor does not mean every installation operates at that value.
Also, a power factor of 0.8 does not mean the generator loses 20% of its fuel energy. Power factor and generator efficiency are different measurements.
Why Both Ratings Matter
Consider a generator rated 100 kVA / 80 kW. A higher load power factor does not automatically increase its rated real power output to 100 kW.
The installation must stay within both the generator set’s kW limit and the alternator’s permitted current and kVA limits. Checking only one rating can overlook a capacity limit.
Does a 100 kW Load Need a 125 kVA Generator?
At an assumed load power factor of 0.8:
100 kW ÷ 0.8 = 125 kVA
This establishes the running apparent power demand. It does not confirm that a 125 kVA generator is sufficient for the installation.
Final diesel generator sizing should also consider:
- Motor starting requirements and load sequencing.
- Acceptable voltage and frequency dips when loads connect.
- UPS systems, variable frequency drives and other nonlinear loads.
- Required duty, operating hours and future expansion.
When comparing quotations, check whether the stated capacities are prime or standby ratings and match them to the intended use.
Choosing a Diesel Generator for UAE Conditions
For a UAE installation, confirm the generator’s available output at the specified site temperature and installation conditions.
High cooling-air temperatures can require alternator derating. Ask whether the quoted rating already includes the required temperature adjustment, rather than applying a generic reduction twice. Cooling and ventilation arrangements should also be reviewed.
Frequently Asked Questions
How Many kW Is a 100 kVA Generator?
At a rated power factor of 0.8, 100 kVA corresponds to 80 kW. Confirm the generator’s stated kW rating and duty in its datasheet.
Are kW and kVA Equal?
They are numerically equal at a power factor of 1.0. This does not remove the generator’s rated kW limit.
Should I Choose a Generator by kW or kVA?
Check both, together with starting loads, operating conditions and the required rating category.
Find the Right Generator with MYSPAN
Need help selecting a Kirloskar diesel generator for your project? Share your equipment load list, starting requirements, operating hours and site location with MYSPAN Power Solutions.
Contact MYSPAN to discuss your power requirements and request a generator quotation.