1. What is an Electric Generator Size Calculator?

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

Purpose: It helps homeowners, contractors, and facility managers determine the appropriate generator capacity for backup power needs.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( P_{kW} \) — Generator size (kilowatts)
• \( \Sigma P_{load} \) — Total electrical load (watts)
• \( SF \) — Safety factor (typically 1.25 for generators)

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 wattage of all connected loads and the safety factor (default 1.25). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why do we need a safety factor?
A: The safety factor accounts for motor startup currents (which can be 3-5x running current) and potential future load additions.

Q2: How do I find my total load?
A: Sum the wattage of all devices to be powered simultaneously, or use nameplate ratings on equipment.

Q3: When would I change the safety factor?
A: Use higher factors (1.5-2.0) for heavy motor loads or critical applications. Use lower factors (1.1-1.2) for resistive loads only.

Q4: Should I include all household circuits?
A: Only include essential circuits you want to power during an outage. Typical essentials include refrigeration, lighting, and communication devices.

Q5: Does this include generator efficiency losses?
A: No, consider that most generators operate at 80-90% efficiency when running at rated capacity.