Generator Size Calculator
Calculate the right generator size by entering your appliance details below.
List of the Top 10 Best Generators:
How to Size a Generator Correctly?
Common Load Types and Wattages
| Appliance | Running Watts | Starting Watts |
|---|---|---|
| Refrigerator | 700 | 2,200 |
| Sump Pump | 800 | 2,400 |
| Well Pump | 1,000 | 3,000 |
| Window AC | 1,200 | 3,600 |
| Clothes Dryer | 5,400 | 6,750 |
| Central AC (3 ton) | 3,500 | 10,500 |
Generator Size Categories
| Generator Size | Typical Applications | Common Uses |
|---|---|---|
| Small (2,000-4,000W) | Camping, Tailgating | Small appliances, Lights, TV |
| Medium (4,000-8,000W) | Home Backup, RV | Essential appliances, Small AC |
| Large (8,000-15,000W) | Whole House | Multiple appliances, Central AC |
| Industrial (15,000W+) | Commercial, Industrial | Heavy equipment, Large facilities |
Important Considerations When Sizing a Generator
1. Power Quality Requirements
Different applications require different power quality levels:
- Standard Generators:
- Good for resistive loads (heaters, lights)
- Suitable for basic tools and appliances
- More affordable option
- Inverter Generators:
- Clean power for electronics
- Better fuel efficiency
- Quieter operation
- More expensive
2. Fuel Type Considerations
Choose the right fuel type based on your needs:
- Gasoline:
- Most common for portable units
- Readily available
- Shorter shelf life
- Propane:
- Longer shelf life
- Cleaner burning
- Lower power output
- Diesel:
- Better fuel efficiency
- Longer runtime
- Better for larger units
- Dual Fuel:
- More flexibility
- Backup fuel option
- Higher initial cost
3. Runtime and Fuel Efficiency
Consider operational duration needs:
- Calculate fuel consumption at expected load
- Consider fuel tank size
- Plan for refueling intervals
- Account for fuel availability during emergencies
4. Environmental Factors
Account for installation location and conditions:
- Altitude derating (3.5% per 1,000 ft above 3,000 ft)
- Temperature impact on performance
- Noise restrictions in your area
- Weather protection requirements
Generator Safety and Maintenance
Essential Safety Guidelines
- Installation:
- Proper ventilation - at least 20 feet from buildings
- Protection from weather
- Secure mounting when required
- Proper grounding
- Operation:
- Never operate indoors
- Keep away from open windows
- Use proper extension cords
- Don't exceed rated capacity
- Maintenance:
- Regular oil changes
- Air filter cleaning/replacement
- Spark plug maintenance
- Fuel system maintenance
Frequently Asked Questions
How do I determine my generator needs?
Start by listing all appliances you need to power, noting both running and starting watts. Use our calculator above to add these up, including a 20% safety margin. Consider which items need to run simultaneously and any future needs.
What's the difference between running watts and starting watts?
Running watts is the continuous power an appliance needs to operate. Starting watts is the extra power needed to start motor-driven appliances, often 2-3 times the running watts. Your generator must handle the highest combination of both.
Should I get a larger generator than I need?
It's recommended to include a 20% safety margin above your calculated needs. This accounts for:
- Future additional appliances
- Unexpected power demands
- Generator efficiency loss over time
- Altitude and temperature derating
How often should I maintain my generator?
Regular maintenance depends on usage but typically includes:
- Oil change every 50-100 hours of use
- Air filter check/clean every 25 hours
- Spark plug check every 100 hours
- Annual professional inspection
What about commercial and industrial applications?
Commercial and industrial generators require special considerations:
- Professional load calculation
- Three-phase power requirements
- Redundancy needs
- Local codes and permits
- Professional installation