kVA (Kilovolt-Ampere)
Definition
Kilovolt-ampere (kVA) is a unit of apparent power in an AC electrical system, calculated as voltage × current ÷ 1,000. Unlike kilowatts (kW), which measure real power (actual work performed), kVA represents the total power flowing through the circuit including both real power and reactive power. The relationship is: kW = kVA × Power Factor. For purely resistive loads (heaters, incandescent bulbs), power factor is 1.0 and kVA equals kW. For inductive loads (motors, transformers), power factor is typically 0.8–0.9, so kVA is higher than kW. Generators and transformers are rated in kVA because they must handle the full apparent power.
Why is kVA (Kilovolt-Ampere) Important?
In electrical engineering and everyday applications, kVA (Kilovolt-Ampere) is a fundamental concept for understanding how electrical systems work. Whether you are an engineer designing circuits, an electrician sizing wires, or a homeowner estimating energy costs, this metric is essential for safety, efficiency, and accurate calculations.
Our electrical conversion calculators help you quickly convert between units and verify calculations, reducing errors and saving time in both professional and DIY electrical work.
What is kVA?
kVA (kilovolt-ampere) is a unit of apparent power — the total power flowing in an AC electrical circuit, combining both the real power (that does useful work) and reactive power (that sustains electromagnetic fields in motors and transformers). It is the primary rating unit for generators, transformers, and UPS systems.
kVA vs kW
| Metric | Unit | Represents | Billing |
|---|---|---|---|
| kVA (Apparent Power) | Kilovolt-Amperes | Total power in the circuit | Used to size generators, transformers |
| kW (Real Power) | Kilowatts | Power actually doing work | What you pay for on your electric bill |
| kVAR (Reactive Power) | Kilovolt-Amps Reactive | Power sustaining magnetic fields | Penalty if power factor is too low |
Relationship: kW = kVA × Power Factor (PF)
Generator Sizing Guide
| Generator kVA | kW at PF 0.80 | Suitable For |
|---|---|---|
| 3 kVA | 2.4 kW | Small portable — camping, basic tools |
| 5 kVA | 4 kW | Portable — essentials during power outage |
| 10 kVA | 8 kW | Portable — most home circuits during outage |
| 22 kVA | 17.6 kW | Whole-house standby generator |
| 50 kVA | 40 kW | Small commercial, construction site |
| 100 kVA | 80 kW | Medium commercial building |
Transformer kVA Ratings
| Transformer kVA | Max Amps (at 240V single-phase) | Typical Use |
|---|---|---|
| 15 kVA | 62.5 A | 1–2 residential homes |
| 25 kVA | 104 A | 2–4 homes |
| 50 kVA | 208 A | Small commercial, 5–10 homes |
| 100 kVA | 416 A | Medium commercial, apartment building |