Electrical Design -⚡ Understanding Active Power vs. Apparent Power (Made Simple)
- MTS DNC ENERGY CONSULTANTS LIMITED
- Oct 26
- 2 min read
Updated: Oct 27
Electrical power isn’t always straightforward — not all the electricity you draw is actually used to do work. Let’s break it down 👇
🔹 Active Power (P) – The Useful Power
This is the real, usable power that does actual work — like heating, lighting, or running a motor.
Unit: Watts (W)
Formula: P = V × I × cosφ
Example 1:💡 A 100W light bulb uses 100W of active power.All the power is converted into light and heat — simple and efficient.
Example 2:🌀 A 2kW electric heater uses 2,000W of active power.Everything goes into heating the air, with no wasted reactive component.
🔹 Apparent Power (S) – The Total Power
This includes both the useful (active) power and the wasted (reactive) power caused by magnetic and electric fields in devices like motors and transformers.
Unit: Volt-Amperes (VA)
Formula: S = V × I
Example:A motor draws 10A at 230V:S = 230 × 10 = 2,300 VA
If the power factor (cosφ) = 0.8,Then Active Power (P) = 2,300 × 0.8 = 1,840 W
So, only 1,840W is used effectively — the rest (460W equivalent) is reactive energy bouncing back and forth in the circuit.
📐 Power Triangle (Visual Representation)
You can visualize the relationship like this:
➡️ Think of it like a triangle:
Base (P) = Useful, active power
Vertical side (Q) = Reactive, non-useful power
Diagonal (S) = Total or apparent power
🧠 Analogy:
Imagine carrying a heavy box 🧱 across the room:
Active Power (P): The energy that actually moves the box forward.
Reactive Power (Q): The sideways effort that doesn’t move the box — just extra strain.
Apparent Power (S): The total effort your muscles feel.
🎨 Image Concept (for post or infographic)
You can create (or I can generate) a clean educational visual showing:
A power triangle labeled P, Q, and S
An electric motor showing the difference between drawn (VA) and useful (W) power
A light bulb vs. motor side-by-side (to illustrate pure active vs. mixed power)
A pie chart showing 80% useful (active) and 20% reactive power
🏗️ Why It Matters in M&E Design
Helps correctly size transformers, cables, and circuit breakers
Improves energy efficiency
Reduces electricity bills by improving power factor
For inquiries or expert guidance, feel free to contact us.
Disclaimer: The content shared in these posts is intended for informational purposes only and should not be interpreted as design advice, specifications, or a calculation template. We disclaim any responsibility or liability for the application of the information provided. For professional guidance or design services, please contact us through our contact form.
