Whole House Generator Size Calculator
Calculate the appropriate size generator needed to power your entire home by entering all your household electrical loads below.
House Information
Major Appliances
Kitchen Appliances
Laundry & Utility
Add Custom Loads
Added Custom Loads
List of the Top 10 Best Whole House Generator:
About Whole House Generator Sizing
Selecting the right size generator for your entire home is a critical decision that ensures reliable backup power for all your electrical needs. Our calculator helps you determine the appropriate generator capacity based on your specific household requirements.
Whole House Generator Size Guide
| Generator Size | Home Size | Typical Coverage |
|---|---|---|
| 22-25 kW | Up to 3,000 sq ft | Full house with standard amenities |
| 30-36 kW | 3,000-5,000 sq ft | Large home with multiple HVAC units |
| 40-48 kW | 5,000+ sq ft | Luxury home with all amenities |
| 50-60 kW | Estate homes | Complete power for largest residences |
Common Household Power Requirements
| Appliance | Running Watts | Starting Watts |
|---|---|---|
| Central AC (3 Ton) | 6,000W | 15,000W |
| Electric Furnace (15kW) | 15,000W | 15,000W |
| Electric Water Heater | 4,500W | 4,500W |
| Electric Range | 8,000W | 8,000W |
| Electric Dryer | 5,400W | 6,500W |
| Well Pump (1 HP) | 2,100W | 6,300W |
| Refrigerator | 700W | 2,200W |
Essential Considerations for Whole House Generators
1. Load Management Systems
Modern whole house generators often include smart load management systems that:
- Automatically prioritize essential appliances
- Manage load shedding during peak demands
- Optimize generator performance and fuel efficiency
- Allow customization of power distribution
- Monitor and protect against overload conditions
2. Installation Requirements
Installing a whole house generator requires careful planning:
- Professional Assessment:
- Site evaluation and load calculation
- Electrical service compatibility check
- Fuel source availability assessment
- Local code compliance review
- Infrastructure Needs:
- Concrete pad or platform installation
- Automatic transfer switch installation
- Fuel line installation or tank placement
- Electrical system modifications
3. Fuel Options and Considerations
| Fuel Type | Advantages | Considerations |
|---|---|---|
| Natural Gas | Unlimited supply, lower cost, clean burning | Requires existing gas line, utility dependent |
| Liquid Propane | Clean burning, long storage life | Requires tank installation, regular refills |
| Diesel | Efficient, widely available | Fuel storage, maintenance needs |
Operating Costs and Maintenance
Annual Operating Costs
- Fuel Consumption:
- Natural Gas: $150-300 per year
- Propane: $200-400 per year
- Diesel: $250-500 per year
- Maintenance Costs:
- Regular service: $200-400 annually
- Parts replacement: $100-300 per year
- Professional inspections: $150-300 per visit
Maintenance Schedule
- Monthly Tasks:
- Test generator operation
- Check fluid levels
- Inspect air intake
- Monitor warning indicators
- Annual Service:
- Oil and filter change
- Battery testing
- Transfer switch inspection
- System diagnostics
Frequently Asked Questions
How do I determine if my generator is large enough for my whole house?
To determine if a generator is adequately sized:
- Calculate total running watts of all appliances
- Account for starting watts of large motors
- Add 20% safety margin for future needs
- Consider load management options if needed
- Verify against your home's electrical service size
Why is my calculated generator size larger than my neighbor's?
Generator size variations between homes occur due to:
- Different electrical service sizes (100A vs 200A)
- Number and size of air conditioning units
- Electric vs gas appliances
- Presence of well pumps or pool equipment
- Total square footage differences
Can I use load management to reduce my generator size?
Yes, load management can help optimize generator size:
- Smart switches can prioritize essential loads
- Non-essential loads can be shed during peak demands
- Can reduce generator size by 25-40%
- Requires professional setup and configuration
How does altitude affect generator sizing?
Generator capacity decreases with altitude:
- 1-3.5% power loss per 1,000 feet above sea level
- May need to upsize generator at high altitudes
- Consult manufacturer's altitude derating tables
- Consider fuel system adjustments for altitude
Should I oversize my generator for future expansion?
Consider future needs when sizing:
- Plan for potential home additions
- Account for future appliance upgrades
- Consider electric vehicle charging
- Add 20-30% capacity for future growth
How do electric vehicle chargers impact generator sizing?
EV charging can significantly affect size requirements:
- Level 1 charging adds 1.5-2.0 kW
- Level 2 charging adds 7.7-11.5 kW
- May need load management for EV charging
- Consider charging speed limitations during outages
What size generator do I need for multiple AC units?
For multiple AC units, consider:
- Combined running watts of all units
- Staggered start-up sequence
- Load management controllers
- Peak demand scenarios
How does climate affect generator sizing?
Climate impacts generator requirements through:
- HVAC load variations
- Seasonal usage patterns
- Generator cooling needs
- Fuel consumption differences
Do I need to include every circuit in my sizing calculations?
Consider these factors when calculating circuits:
- Essential vs non-essential circuits
- Peak load scenarios
- Diversity factor of loads
- Load management possibilities
How do starting watts affect generator sizing?
Starting watts are crucial because:
- Motors require 3-5 times running watts to start
- Multiple devices may start simultaneously
- Generator must handle highest potential surge
- Affects transfer switch requirements
What is load diversity and how does it affect sizing?
Load diversity considerations include:
- Not all appliances run simultaneously
- Peak usage patterns vary throughout day
- Can reduce required generator size
- Typical diversity factor is 0.6-0.8
Should generator size match my electrical service size?
Service size matching factors:
- Generator can be smaller than service size
- Consider actual power usage patterns
- Load management can reduce size needs
- Match transfer switch to service size
How do medical devices affect generator sizing?
Medical equipment considerations:
- Include backup power requirements
- Account for continuous operation
- Add redundancy for critical devices
- Consider UPS backup systems
What's the impact of motor loads on generator sizing?
Motor loads require special consideration:
- Starting current requirements
- Sequence of motor starts
- Voltage drop limitations
- Load management strategies
How do I account for seasonal load variations?
Seasonal considerations include:
- Peak summer cooling loads
- Winter heating requirements
- Seasonal equipment usage
- Size for highest seasonal demand