1. What is a Commercial Generator Size Calculator?

Definition: This calculator estimates the required generator size in kilowatts (kW) based on the total electrical load and a safety factor.

Purpose: It helps facility managers, electricians, and contractors properly size commercial generators for backup power systems.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( P_{kW} \) — Generator size (kilowatts)
• \( P_{load} \) — Total electrical load (watts)
• \( SF \) — Safety factor (typically 1.5–2.0)

Explanation: The total load in watts is converted to kilowatts (divided by 1000) then multiplied by a safety factor to account for startup surges and future expansion.

3. Importance of Proper Generator Sizing

Details: Correct generator sizing ensures reliable power during outages, prevents overload conditions, and maximizes fuel efficiency.

4. Using the Calculator

Tips: Enter the total connected load in watts and safety factor (default 1.75). The safety factor should be between 1.0 and 3.0.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical safety factor for commercial generators?
A: Most commercial applications use 1.5–2.0, with 1.75 being common for mixed loads.

Q2: How do I find my total electrical load?
A: Sum the wattage of all connected equipment or check your electrical panel's main breaker rating.

Q3: When would I use a higher safety factor?
A: For motor-heavy loads (HVAC, elevators) or critical systems (hospitals, data centers) where startup surges are significant.

Q4: Does this include three-phase calculations?
A: This provides basic sizing. For three-phase systems, consult an electrician for precise calculations.

Q5: Should I round up the generator size?
A: Yes, always round up to the next standard generator size available from manufacturers.