Whole House Generator Sizing Calculator
What appliances do you need to run during a power outage? Select items below to calculate your required wattage and find the perfect generator size for your home.
Total Load Calculation
Includes 20% safety margin + highest surge
Quick Sizing Guide
Complete Generator Sizing Guide
Understanding Generator Sizing
Proper generator sizing requires calculating both your running watts (continuous power draw) and starting watts (surge power needed when motors start). Our calculator automatically accounts for the highest surge requirement and adds a 20% safety margin.
Key Sizing Concepts:
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Running Watts: The continuous power an appliance uses during normal operation
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Starting Watts: Extra power needed for 1-3 seconds when motors start (can be 2-3x running watts)
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Safety Margin: 20% buffer above calculated needs to prevent overload and extend generator life
Generator Size Categories
Small (7-14kW)
Best for apartments, condos, small homes
- • Essentials only
- • Fridge, lights, furnace
- • No central AC
- • 1-2 bedrooms
Medium (14-20kW)
Most popular for average homes
- • Most appliances
- • May include AC
- • 2-3 bedrooms
- • Standard comfort
Large (20-26kW)
For large homes, full power
- • Whole house coverage
- • Central AC included
- • 3+ bedrooms
- • All modern conveniences
Common Appliance Wattages
| Appliance | Running Watts | Starting Watts |
|---|---|---|
| Refrigerator | 700W | 2,200W |
| Central AC (3 Ton) | 3,500W | 10,500W |
| Sump Pump (1/2 HP) | 1,050W | 2,150W |
| Electric Dryer | 3,000W | 3,000W |
| Microwave (1000W) | 1,000W | 1,500W |
Note: Appliances with motors (AC, pumps, refrigerators) have high starting watts due to inrush current. Heating elements (dryers, ovens) have minimal surge.
Frequently Asked Questions
Q: What size generator do I need for a 2000 sq ft house?
A: For a typical 2000 sq ft home, a 14-20kW generator is usually sufficient. This assumes you want to run essentials plus some comfort items like AC. If you have central AC and want whole-house coverage, go with 18-22kW. Use our calculator above for a precise estimate based on your actual appliances.
Q: Can I run my whole house on a 22kW generator?
A: A 22kW generator is the most popular whole-house size and can power most 2,500-3,000 sq ft homes with central AC. However, you may need to manage loads - avoid running all high-wattage appliances simultaneously. For unrestricted usage in larger homes or with multiple AC units, consider 24-26kW.
Q: What's the difference between air-cooled and liquid-cooled generators?
A: Air-cooled generators (up to 26kW) are less expensive, easier to maintain, and sufficient for most homes. Liquid-cooled generators (30-150kW) are for large homes or commercial use, run quieter, last longer, and handle extended outages better, but cost significantly more ($10,000-30,000+ installed).
Pro Sizing Tips
- Don't undersize: It's better to have 20% extra capacity than to struggle during outages. Undersized generators work harder and wear out faster.
- Plan for the future: Consider appliances you might add in the next 5-10 years. It's cheaper to buy a larger generator now than to upgrade later.
- Consider load management: With automatic load shedding, you can run a larger home on a smaller generator by prioritizing critical circuits.