How to Calculate Electrical Load
What is Electrical Load?
Electrical load calculation determines service size, feeder, and branch circuit requirements. Under-sizing risks overheating; over-sizing wastes cost.
Step-by-Step Guide
- 1Sum connected loads and apply demand factors per code
- 2Typical demand factors: lighting 100%, HVAC 100%, convenience outlets 50-100%
- 3Size service for total demand + margin for future growth
Worked Examples
Input
Lighting 50 kW, HVAC 150 kW, outlets 30 kW, motors 100 kW
Result
Total demand ≈ 270 kW + 25% margin = 338 kW service
Code-compliant sizing
Common Mistakes to Avoid
- ✕Using connected load without demand factors
- ✕Neglecting motor inrush current effects
Frequently Asked Questions
Why use demand factors?
Not all loads run simultaneously; factors reflect realistic concurrent usage patterns.
Should future growth be included?
Yes, typically 20-25% margin allows expansion without service upgrade.
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