1. What is Generator Sizing?

Generator sizing is the process of determining the appropriate wattage capacity for a generator based on the total electrical load it needs to support, plus a safety factor to account for startup surges and future expansion.

2. How Does the Calculator Work?

The calculator uses the generator sizing formula:

Where:

• \( P_{total} \) — Recommended generator size in watts
• \( \sum P_{loads} \) — Sum of all electrical loads in watts
• \( 1.2 \text{ to } 1.5 \) — Safety factor (1.2 for minimal, 1.35 recommended, 1.5 for maximum)

Explanation: The safety factor accounts for startup current surges (especially for motors) and provides headroom for future additions.

3. Importance of Proper Generator Sizing

Details: Proper generator sizing ensures reliable operation, prevents overload conditions, maximizes fuel efficiency, and extends equipment life. Undersized generators may fail during startup surges, while oversized ones operate inefficiently.

4. Using the Calculator

Tips:

1. Calculate the sum of all electrical loads (in watts) that will run simultaneously
2. Select appropriate safety factor (1.35 recommended for most applications)
3. Consider future expansion when choosing generator size
4. For motor loads, use the starting wattage (not running wattage) in your calculations

5. Frequently Asked Questions (FAQ)

Q1: Why is a safety factor needed?
A: Electrical devices (especially motors) often require 2-3 times their running wattage during startup. The safety factor ensures the generator can handle these temporary surges.

Q2: What's the difference between 1.2 and 1.5 safety factor?
A: 1.2 is minimal for known loads with no future expansion. 1.35 is standard for typical applications. 1.5 provides maximum headroom for uncertain loads or future expansion.

Q3: Should I size for running watts or starting watts?
A: Size for the highest possible demand - typically the sum of all starting watts for devices that might start simultaneously.

Q4: How do I account for three-phase equipment?
A: For three-phase loads, use the formula: Watts = Volts × Amps × 1.732 × Power Factor. Consult an electrician for complex three-phase systems.

Q5: What about generator efficiency?
A: Most generators are most efficient at 50-80% load. Oversizing beyond 1.5× your calculated need may reduce efficiency and increase fuel consumption.