Publish Time: 2025-06-27 Origin: Site
Ever wondered why your 100 kW generator isn’t enough? It might be a power factor issue.
kW measures real power. kVA shows total power used—including waste. They’re not always the same.
Understanding the difference is key when sizing equipment like generators, transformers, and UPS systems.
In this post, you'll learn what kW and kVA mean, why they matter, and how to convert between them.
Let's break it down: kW stands for kilowatts, and it's the real power. This is the part of electricity that actually does useful work—like spinning a fan or lighting up a bulb.
On the other hand, kVA, or kilovolt-amperes, is apparent power. It includes both the real power and some extra power that doesn't do work but still flows through the system. That extra part is called reactive power.
So, think of kW as the power you use. kVA is what your system draws from the source. They're related but not equal in most AC systems.
Why does this matter? Well, if you're sizing a generator, motor, or transformer, this difference helps avoid overloads and failure.
Here’s where the power factor (PF) steps in. It’s the link between kW and kVA.
Power factor is a number from 0 to 1. It tells you how much of the electricity is doing actual work. A PF of 1 means all the power is useful. But that’s rare.
In real life, most systems run at 0.8 PF. Motors, HVAC units, and computers usually cause a PF below 1 because they store and return energy instead of using it all.
That’s why:
If your system needs 100 kW at a 0.8 PF, you actually need 125 kVA to support it. So, a lower power factor means a higher kVA for the same kW.
kVA = kW ÷ PF
Here's a table to make things clear:
| Parameter | kW (Kilowatt) | kVA (Kilovolt-Ampere) |
|---|---|---|
| Power Type | Real (working) power | Apparent (total) power |
| Formula | kW = Voltage × Current × PF | kVA = Voltage × Current |
| Includes PF? | Yes | No |
| Used For | Energy bills, real work done | Equipment sizing like UPS, generators |
| Always Equal? | Only when PF = 1 | Often more than kW in AC systems |
| Common Value in AC | Lower due to PF < 1 | Higher because it includes wasted energy |
Just remember: if kW is what gets the job done, kVA is the full ride your system takes—bumps and all.
Here’s the basic rule: kVA = kW ÷ PF
It looks simple, but each part matters:
kW (Kilowatt): the real power that does useful work.
kVA (Kilovolt-Ampere): the total power drawn by a system.
PF (Power Factor): the efficiency factor, usually between 0.7 and 1.
This formula helps when designing systems like generators, transformers, or UPS units.
If you know the power factor and your equipment’s power need in kW, you can find the required apparent power (kVA) using this formula.
Let’s try a few easy ones so you get the hang of it.
Power factor = 0.8
kVA = 10 ÷ 0.8 = 12.5
Power factor = 0.9
kVA = 100 ÷ 0.9 = 111.1
Let’s say your motor uses 60 kW, and PF = 0.85
kVA = 60 ÷ 0.85 = 70.6
This means the motor needs 70.6 kVA of supply even though it only uses 60 kW to work.
Sometimes, you’ll have kVA and need to get back to kW. Just flip the formula:
kW = kVA × PF
Let’s do one:
You have a 90 kVA UPS system
Power factor is 0.9
kW = 90 × 0.9 = 81
So, your UPS delivers 81 kW of real power. The rest is reactive power or system losses.
Engineers use kW to kVA conversion all the time. It’s not just math—it’s about getting the job done right.
Electrical system sizing depends on it. If you oversize, you waste money. If you undersize, things break.
When choosing a transformer, knowing the apparent power (kVA) helps pick the right size.
Need a generator? Its rating is in kVA. But your load is often listed in kW. So, yes—you’ll have to convert.
Let’s look at how different industries apply this conversion in real life.
Imagine your building needs 80 kW during an outage. The power factor is 0.8.
To find the right generator size:
kVA = 80 ÷ 0.8 = 100 kVA
You’ll need a generator rated at least 100 kVA to handle that.
Data centers often run at 90 kW and have PF ≈ 0.9.
To size a UPS:
kVA = 90 ÷ 0.9 = 100 kVA
That ensures enough capacity without overload or shutdown.
HVAC units are notorious for poor power factor. Say your AC uses 60 kW and PF = 0.85.
You’d need:
kVA = 60 ÷ 0.85 = 70.6 kVA
That extra 10.6 kVA is power the AC draws but doesn’t convert into cooling.
Let’s say a motor pulls 75 kW. Power factor is 0.88 (typical for motors).
Required input:
kVA = 75 ÷ 0.88 = 85.2 kVA
So, while the motor outputs 75 kW of work, it still pulls over 85 kVA from the grid.
| Application | Real Power (kW) | Power Factor (PF) | Required kVA |
|---|---|---|---|
| Backup Generator | 80 | 0.8 | 100 |
| Data Center UPS | 90 | 0.9 | 100 |
| HVAC Chiller | 60 | 0.85 | 70.6 |
| Industrial Motor | 75 | 0.88 | 85.2 |
Need a quick reference for converting kilowatts to kilovolt-amperes? Here’s a handy chart.
We’ve based this table on a power factor (PF) of 0.8, which is common in most industrial and commercial setups.
Just find your kW value, and you’ll see how much apparent power (kVA) your system needs to deliver.
| kW (Real Power) | kVA (Apparent Power) |
|---|---|
| 1 | 1.25 |
| 5 | 6.25 |
| 10 | 12.5 |
| 20 | 25 |
| 50 | 62.5 |
| 75 | 93.75 |
| 100 | 125 |
| 150 | 187.5 |
| 200 | 250 |
| 250 | 312.5 |
| 300 | 375 |
| 400 | 500 |
| 500 | 625 |
| 600 | 750 |
| 700 | 875 |
| 800 | 1000 |
| 900 | 1125 |
| 1000 | 1250 |
| 1250 | 1562.5 |
| 1500 | 1875 |
| 1750 | 2187.5 |
| 2000 | 2500 |
The values above are based on PF = 0.8, but systems vary. You might need to tweak your numbers.
Here’s how to adjust it:
For PF = 0.9, divide your kW by 0.9.
For PF = 0.7, divide by 0.7.
Use the formula:
kVA = kW ÷ PF
If you’ve got a 30 kW motor at PF = 0.9, here’s what to do:
kVA = 30 ÷ 0.9 = 33.3
Lower PF? Your system pulls more kVA to get the same work done.
These calculators are super handy—just plug in two numbers, and you’re done.
Most tools ask for:
kW (Real Power)
Power Factor (PF)
Once you hit “Calculate,” it gives you kVA, which is the apparent power your system requires.
Here’s what the output means:
It shows how much total power your equipment will draw.
Even if some of it isn’t used for real work, your system still needs to supply that power.
Don’t guess the power factor. Use the actual value from your equipment.
These tools don’t calculate reactive power (kVAR) unless stated.
If you use the wrong PF, your result might oversize—or worse—undersize your system.
Great for quick checks, not full engineering specs.
You don’t need fancy software. These online calculators get the job done fast.
Clean design, easy inputs
Shows step-by-step math
Great for students and engineers
Built for quick electrical unit conversions
Includes conversions for kW, kVA, and power factor
Ideal for engineers and technicians to size equipment quickly
| Tool Name | Best For | Link |
|---|---|---|
| Inch Calculator | Quick math + user-friendly | Visit |
| RapidTables Calculator | Power calculations + General unit conversions | Visit |
Just enter your numbers—let the tool handle the rest.
It depends on the power factor (PF).
Use the formula:
kVA = kW ÷ PF
If PF = 0.8, then:
kVA = 1 ÷ 0.8 = 1.25
So, 1 kW = 1.25 kVA at 0.8 PF.
But if PF = 1 (like in DC systems), then:
kVA = 1 ÷ 1 = 1
Let’s go step-by-step using PF = 0.8 (standard in many cases).
Step 1: Write the formula
kVA = kW ÷ PF
Step 2: Plug in your values
kVA = 500 ÷ 0.8 = 625
So, 500 kW needs 625 kVA if the PF is 0.8.
Change the PF? You’ll get a different result.
Yes—unless your power factor is 1, which is rare in AC systems.
Because:
kW = power used to do actual work
kVA = total power flowing in the system
Since not all power becomes useful, kW is usually lower.
Example:
100 kW ÷ 0.8 = 125 kVA
Most industrial machines don’t run at PF = 1. They use motors, pumps, and compressors, which lower the PF.
Here’s a quick reference:
| Equipment | Typical PF |
|---|---|
| Motors | 0.85–0.9 |
| HVAC Systems | 0.8–0.9 |
| Data Centers | 0.9–0.95 |
| Resistive Loads | ~1.0 |
Unless you're using heaters or incandescent lamps, expect PF < 1.
No need to convert in DC circuits. Why?
Because power factor is always 1 in DC. There’s no phase shift between voltage and current.
So:
kW = kVA
If you have a DC load, 10 kW is just 10 kVA. No adjustments required.
This is the most common mistake people make.
They just assume kW = kVA, which only works when power factor (PF) = 1—rare in real life.
In most AC systems, PF ranges between 0.7 to 0.95. Ignoring it leads to underpowered equipment or system overloads.
Always use the formula:
kVA = kW ÷ PF
Even a small error in PF can change the result by a lot.
Using "average" numbers like 0.8 or 0.9 might seem easy, but it’s risky.
Your real-world PF could be lower due to aging equipment, poor load management, or lack of correction.
If you guess the PF:
You might oversize the system = wasted money
You might undersize it = breakdowns
Tip: Check manufacturer specs or measure PF using a meter.
Resistive loads (like heaters, incandescent bulbs) have a PF close to 1.
Inductive loads (like motors, compressors, HVAC units) often run at PF below 1.
If you treat them the same, the conversion goes wrong.
| Load Type | Power Factor | Conversion Notes |
|---|---|---|
| Resistive | ~1.0 | kW ≈ kVA, simple conversion |
| Inductive | 0.7 – 0.9 | Must use formula, higher kVA needed |
| Capacitive | Varies | May need PF correction |
Before converting, always ask: “What kind of load am I dealing with?”
Need to go beyond kW to kVA? These tools help calculate other electrical values quickly.
Figure out how much current your device draws, based on voltage and power. Great for cable sizing.
Helps you understand voltage drops or find missing values in circuits using Ohm’s Law.
Need to convert from amps and volts to watts? This tool does it in one click.
| Calculator | Use Case | Try It Here |
|---|---|---|
| Amp Calculator | Sizing wires, circuit breakers | Amp Calculator |
| Volt Calculator | Voltage drop, unknown voltage | Volt Calculator |
| Watt Calculator | Convert amps + volts to watts | Watt Calculator |
If you’re digging into conversions, it helps to understand how electrical systems actually work.
Got a low PF? You’re wasting energy. Learn how capacitor banks improve it, and how that cuts your energy costs.
kW is real. kVAR is reactive. Know the difference, so you can measure what truly matters in your system.
Before you buy a generator, plan your load. Learn how to calculate total demand, avoid overload, and ensure system safety.
| Topic | What You'll Learn |
|---|---|
| Power Factor Correction | How to improve system efficiency |
| Real vs. Reactive Power | What power does work vs. what bounces around |
| Load Planning | How to size your system without over/undershooting |
To convert kilowatts (kW) to kilovolt-amperes (kVA), use this simple formula:
kVA = kW ÷ Power Factor (PF)
Just remember:
kW is the real, working power
kVA includes both working and wasted (reactive) power
A lower power factor means more apparent power is needed for the same job.
If you guess your numbers, you risk overloading equipment—or buying something bigger than necessary.
Accurate conversion helps with:
Generator sizing
UPS capacity
Transformer selection
Panel and cable load calculations
It keeps your systems safe, efficient, and cost-effective.
Even pros double-check their numbers. Why not you?
Use reliable tools to speed up your work:
| Resource | Use Case | Link |
|---|---|---|
| kW to kVA Calculator | Convert fast with built-in PF options | Use Tool |
| Amp/Volt/Watt Calculators | Solve other electric formulas easily | Browse Tools |
| Learn About kVA to amps | Boost system efficiency | Read More |
| Learn About kVA to kW | Deep dive into power types | Explore Topic |