Demand Factor means:

How much electrical load is actually used compared to the total connected load.

📌 Formula

$$\text{Demand Factor} = \frac{\text{Maximum Demand}}{\text{Total Connected Load}}$$Demand Factor=Total Connected LoadMaximum Demand​

🔌 Simple Example

Suppose in a building:

• 10 lights = 10 × 100 W = 1000 W
• 2 AC = 2 × 1500 W = 3000 W
• 1 Heater = 2000 W

👉 Total Connected Load = 6000 W

But not all devices run at the same time.
Maybe the maximum load used at one time = 4000 W

So,$$\text{Demand Factor} = \frac{4000}{6000} = 0.67$$Demand Factor=60004000​=0.67

👉 Demand Factor = 0.67 (or 67%)

💡 In One Line

Demand Factor = Actual maximum power used ÷ Total installed power

🏢 Why Engineers Use It

Electrical engineers use demand factor to:

• Size transformers
• Design cables
• Calculate maximum load
• Design switchgear

Because all equipment will not run together.

⚡ Real Example (Apartment)

But maximum demand maybe only 12 kW

Demand Factor = 12 / 18 = 0.67

✅ Important Point:
Demand Factor is always ≤ 1

It can never be greater than 1.

Whta is Demand Load (Simple Explanation)

Demand Load means:

The actual electrical power required by equipment at a particular time.

It is the load that is really being used, not the total installed load.

🔌 Simple Example

Suppose in a house you have:

👉 Total Connected Load = 4200 W

But at a certain time only:

• Lights = 500 W
• Fans = 200 W
• AC = 1500 W

are running.

So the Demand Load = 2200 W

Because heater is OFF.

📌 In One Line

Demand Load = The power actually used at a specific time.

⚡ Demand Load vs Connected Load

🏢 Example in Building

A building may have:

• Connected Load = 100 kW
• But normally only 60 kW is used

👉 Demand Load = 60 kW

💡 Why It Is Important

Electrical engineers use Demand Load to decide:

• Transformer size
• Cable size
• Generator capacity
• Switchgear rating

✅ Very Short Definition:
Demand Load = Actual electrical load used at a given time.

reat! Let’s understand the 3 very important electrical load terms used in electrical design and SLD calculations. I’ll keep it very simple. ⚡

1️⃣ Connected Load

Connected Load means:

Total power of all electrical equipment installed.

Even if the equipment is ON or OFF, it is still counted.

Example

👉 Connected Load = 10 kW

All equipment power added together.

2️⃣ Demand Load

Demand Load means:

The load actually used at a particular time.

Not all equipment runs at the same time.

Example

At a certain time only:

• Lights = 2 kW
• Fans = 1 kW
• AC = 5 kW

👉 Demand Load = 8 kW

Heater is OFF, so it is not counted.

3️⃣ Maximum Demand

Maximum Demand means:

The highest electrical load used at any time in a system.

It is the maximum power the system ever draws.

Example (During a day)

👉 Maximum Demand = 9 kW

Because that is the highest load used.

⚡ Simple Comparison

🏢 How Engineers Use This (SLD Design)

In electrical design:

1. First calculate Connected Load
2. Apply Demand Factor
3. Find Maximum Demand
4. Then size:
   • Transformer
   • Cables
   • Switchgear

✅ Example

Connected Load = 100 kW
Demand Factor = 0.7

Maximum Demand =
100 × 0.7 = 70 kW

💡 Since you are learning electrical SLD and load calculation, I can also show you a very practical step-by-step method engineers use:

Source → Transformer → Panel → Load calculation