Standby Generator Size Calculator
Calculate the right standby generator size by selecting the appliances and systems you need to power during an outage.
List of the Top 10 Best Standby Generators:
How to Size a Standby Generator?
Understanding Standby Generator Requirements
Proper sizing of a standby generator is crucial for reliable backup power. Consider these key factors:
- Essential Loads:
- HVAC systems (heating, cooling)
- Water systems (well pump, water heater)
- Critical appliances (refrigerator, freezer)
- Security and communication systems
- Power Requirements:
- Running watts for continuous operation
- Starting watts for motor-driven appliances
- Simultaneous operation needs
- Future expansion considerations
Common Standby Generator Sizes
| Generator Size | Home Size | Typical Coverage | Best For |
|---|---|---|---|
| 14-16 kW | Up to 2,500 sq ft | Essential circuits | Small to medium homes |
| 20-22 kW | 2,500-3,500 sq ft | Most circuits | Medium to large homes |
| 24-30 kW | 3,500-5,000 sq ft | Whole house | Large homes |
| 36-48 kW | 5,000+ sq ft | Complete coverage | Luxury homes |
Common Appliance Power Requirements
| Appliance | Running Watts | Starting Watts |
|---|---|---|
| Central AC (3-ton) | 3,500 | 10,500 |
| Heat Pump | 4,700 | 14,100 |
| Water Heater | 4,500 | 4,500 |
| Well Pump | 1,000 | 3,000 |
| Electric Range | 8,000 | 8,000 |
| Electric Dryer | 5,400 | 6,750 |
| Refrigerator | 700 | 2,200 |
Important Installation Considerations
1. Location Requirements
Proper placement is crucial:
- Minimum 5 feet from structure openings
- Clear area for maintenance access
- Level, stable mounting surface
- Proper ventilation space
2. Fuel Selection
Choose the right fuel type:
- Natural gas: Continuous supply, lower cost
- Propane: Storage required, higher energy density
- Consider fuel availability
- Required fuel line capacity
3. Transfer Switch Options
Select appropriate transfer switch:
- Automatic transfer switch recommended
- Service entrance rated when required
- Load management capabilities
- Smart management modules
Frequently Asked Questions
How much does a standby generator cost?
The total cost includes the generator, installation, and accessories. Typical ranges:
- 14-16 kW: $4,000-$6,000 unit cost, $8,000-$12,000 installed
- 20-22 kW: $5,000-$7,000 unit cost, $10,000-$15,000 installed
- 24-30 kW: $7,000-$11,000 unit cost, $12,000-$20,000 installed
- 36+ kW: $12,000+ unit cost, $20,000+ installed
What maintenance is required?
Regular maintenance includes:
- Annual professional service
- Oil changes every 100-200 hours
- Weekly self-test runs
- Battery checks and replacement
- Air filter cleaning/replacement
How long can a standby generator run continuously?
With proper fuel supply and maintenance:
- Natural gas units: Indefinitely with continuous fuel supply
- Propane units: Limited by tank size (500-gallon tank typically lasts 1-2 weeks)
- Regular maintenance intervals must be observed
- Consider load management for extended operation