—— Learn the Real Difference with OWELL Generators
Have you ever wondered why some generator sets are rated in kW while others use kVA?
If you find these power units confusing, you’re not alone.
OWELL Generators will help you understand them in just a few minutes — through an intuitive explanation based on IEC 60034 and ISO 8528 international standards.
1. Four Types of Generator Power — Simplified
Generator power units have different meanings and roles.
Here’s a simple chart that explains everything at a glance:
| Power Type | Unit | Function | Everyday Analogy |
|---|---|---|---|
| Mechanical Power | kWm | Raw engine output power | The total beer in the keg |
| Apparent Power | kVA | Generator’s total capacity | The size of the beer glass |
| Active Power | kW / kWe | Usable working power | The beer you actually drink |
| Reactive Power | kVAR | Power to maintain voltage & field | The foam on top of the beer |
In short:
- kW is the real usable energy.
- kVAR is the supporting power for system stability.
- kVA is the total generator load capacity.
2. The Power Triangle: Understanding kW vs kVA
The relationship between the three powers can be visualized as a right triangle:
kVA (Apparent Power)
/|
/ |
/ |
/ |
kW kVAR (Reactive Power)
Mathematical relationship:
kVA² = kW² + kVAR²
Thus, kVA represents the generator’s total power capacity, which includes both useful power (kW) and reactive power (kVAR).
3. Power Factor — The Efficiency Indicator
Power Factor (cosφ) = kW ÷ kVA
It measures how efficiently electrical power is being used.
In most industrial applications, the standard power factor is 0.8 lagging, which is also the global standard for generator rating.
Example:
- If Power Factor = 0.8 → 100 kVA × 0.8 = 80 kW
- If Power Factor = 0.9 → 100 kVA × 0.9 = 90 kW
👉 A 0.1 increase in power factor can deliver 10% more usable power from the same generator capacity.
4. Three Steps to Choose the Right Generator Size
Step 1: Calculate Total Active Power (kW)
List all equipment loads, classify them as resistive or inductive, and add a 15–20% safety margin.
Step 2: Determine the Power Factor
| Load Type | Example Equipment | Power Factor Range |
|---|---|---|
| Resistive | Lamps, heaters | 0.95–1.0 |
| Inductive | Motors, transformers | 0.5–0.85 |
| Mixed Load | General systems | 0.8–0.85 |
Step 3: Calculate Generator Capacity (kVA)
Formula:
kVA = kW ÷ Power Factor
Example:
If total load = 80 kW and PF = 0.8 → Required generator = 100 kVA
This ensures stable operation and smooth motor starting.
5. Common Sizing Mistakes and How to Avoid Them
| Mistake | Possible Issue | Correct Approach |
|---|---|---|
| Selecting by kW only | Generator undersized, startup issues | Size by kVA and include power factor |
| Ignoring load type | Overload or tripping | Consider startup current & reactive demand |
| Neglecting PF impact | Real power lower than expected | Choose generators rated at PF ≥ 0.8 |
6. Power Unit Relationship Summary
kWm (Mechanical Power)
↓ (Efficiency Loss)
kVA (Apparent Power) = √(kW² + kVAR²)
／
／
kW (Active Power) kVAR (Reactive Power)
Key Formula:
kWe = kVA × Power Factor
7. Professional Generator Sizing Support by OWELL
With extensive engineering experience, OWELL Generators provides end-to-end technical support — from planning and configuration to installation guidance — ensuring every generator operates at its best.
- 🔧 Professional Sizing Guidance: Scientific generator capacity calculations based on load lists and application needs.
- 🧠 Technical Consultation: Expert analysis of power factor, grid connection, and load characteristics to design precise power solutions.
- ⚙️ Installation & Commissioning Support: Assistance for wiring, synchronization, and commissioning to ensure safe and efficient operation.
OWELL is committed to helping customers achieve the ideal balance between safety, reliability, and efficiency in every power solution.
8. Conclusion: Understanding Power Is the Key to Proper Sizing
Understanding kW, kVA, and kVAR is like knowing how to pour the perfect beer:
kW is the energy you use,
kVA is the total capacity,
and kVAR is the invisible force keeping the system stable.
With decades of experience in the power generation industry, OWELL not only provides high-quality diesel and gas generator sets, but also delivers professional and scientific power guidance for every project.
Contact OWELL’s professional team for free generator sizing support:
🌐 www.owellgenerators.com/contact
This article is prepared by the OWELL Generators technical team based on IEC 60034 and ISO 8528 standards.
OWELL Generators — Your Trusted Power Solution Expert.
