1. What is a Generator Size Calculator?

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

Purpose: It helps homeowners and professionals select a properly sized generator for backup power needs.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( P_{kW} \) — Generator size (kilowatts)
• \( P_{load} \) — Total wattage of all connected loads (watts)
• \( SF \) — Safety factor (typically 1.2-1.5)

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

3. Importance of Proper Generator Sizing

Details: Correct sizing ensures your generator can handle all connected loads without overload while maintaining efficiency and longevity.

4. Using the Calculator

Tips:

• Sum the wattage of all appliances you want to power simultaneously
• Use safety factor 1.2 for residential, 1.5 for commercial/industrial
• Consider motor starting currents which may require larger capacity

5. Frequently Asked Questions (FAQ)

Q1: What happens if I undersize my generator?
A: An undersized generator may overload, shut down, or fail to start motors, potentially damaging both generator and appliances.

Q2: How do I find appliance wattages?
A: Check nameplates, manuals, or use our Appliance Wattage Calculator. Running watts are typically 1.5-3x rated watts.

Q3: Why is the safety factor important?
A: It accounts for startup surges (especially motors), future expansion, and ensures the generator isn't constantly running at full capacity.

Q4: Should I round up the calculated size?
A: Yes, always round up to the nearest standard generator size available (e.g., 5kW, 7.5kW, 10kW).

Q5: Does this include whole house needs?
A: This calculates based on your input. For whole house, include all essential circuits or use our Whole House Generator Sizing Tool.