Generator Sizing Chart by Square Footage
This chart shows recommended generator sizes based on home size and desired coverage level. Scroll right on mobile to see all columns.
| Square Feet | Essentials Only | Comfortable | Whole Home | Typical Cost |
|---|---|---|---|---|
| Under 1,500 | 10-12 kW | 14-16 kW | 16-18 kW | $6,000-10,000 |
| 1,500-2,000 | 12-14 kW | 16-18 kW | 18-20 kW | $8,000-12,000 |
| 2,000-2,500 | 14-16 kW | 18-20 kW | 20-22 kW | $10,000-14,000 |
| 2,500-3,000 | 16-18 kW | 20-22 kW | 22-24 kW | $12,000-16,000 |
| 3,000-4,000 | 18-20 kW | 22-24 kW | 24-26 kW | $14,000-20,000 |
| 4,000-5,000 | 20-22 kW | 24-26 kW | 26-32 kW | $16,000-25,000 |
| 5,000+ | 22-26 kW | 26-32 kW | 36+ kW | $20,000-35,000 |
* "Comfortable" assumes central AC. Homes with all-electric appliances may need larger sizes.
Understanding Coverage Levels
Essential Coverage
10-14 kWKeep critical systems running
Includes:
- ✓Refrigerator/freezer
- ✓Lights
- ✓Sump pump
- ✓Security system
- ✓A few outlets
Excludes:
- −Central AC
- −Electric water heater
- −Range/oven
- −Dryer
Comfortable Coverage
16-22 kWMaintain normal daily life
Includes:
- ✓Everything essential
- ✓Central AC
- ✓Water heater
- ✓Most outlets
- ✓Kitchen appliances
Excludes:
- −Electric dryer
- −EV charger
- −Pool equipment
Whole Home Coverage
22-36+ kWPower everything, no compromises
Includes:
- ✓All circuits
- ✓All appliances
- ✓EV charger
- ✓Pool/spa
- ✓Workshop
Get Your Exact Size Recommendation
Our calculator asks about your specific appliances and gives you a precise kW recommendation.
Use the CalculatorAppliance Wattage Reference
Use this chart to calculate your total wattage needs. Remember to account for starting wattage for motor-driven appliances—they need a surge of power to start up.
| Appliance | Running (W) | Starting (W) | Priority |
|---|---|---|---|
| Central AC (3-ton) | 3,500 | 4,500 | High |
| Central AC (4-ton) | 4,500 | 6,000 | High |
| Central AC (5-ton) | 5,500 | 7,500 | High |
| Heat pump | 4,500 | 6,000 | High |
| Electric furnace | 10,000 | 10,000 | High |
| Gas furnace blower | 800 | 1,300 | High |
| Electric water heater | 4,500 | 4,500 | Medium |
| Gas water heater | 400 | 400 | Low |
| Refrigerator | 150 | 400 | Essential |
| Freezer (upright) | 100 | 350 | Essential |
| Sump pump (1/3 HP) | 800 | 1,300 | Essential |
| Sump pump (1/2 HP) | 1,050 | 2,150 | Essential |
| Well pump (1/2 HP) | 1,000 | 2,000 | Essential |
| Well pump (1 HP) | 2,000 | 4,000 | Essential |
| Electric range/oven | 3,000 | 3,000 | Medium |
| Microwave (1000W) | 1,000 | 1,000 | Low |
| Dishwasher | 1,500 | 1,500 | Low |
| Clothes washer | 500 | 1,200 | Low |
| Electric dryer | 5,000 | 5,000 | Low |
| Lights (LED, whole home) | 200 | 200 | Essential |
| TV/Entertainment | 200 | 200 | Low |
| Computer/Home office | 300 | 300 | Medium |
| Garage door opener | 550 | 1,100 | Low |
| Security system | 50 | 50 | Essential |
| Electric vehicle charger | 7,500 | 7,500 | Low |
Real-World Sizing Examples
Here's how actual homeowners calculated their generator needs.
2,200 sq ft ranch in Texas
3-ton AC, gas furnace, electric water heater, well pump
AC (4,500W starting) + furnace (1,300W) + water heater (4,500W) + well pump (2,000W) + lights/outlets (1,000W) = 13,300W
1,800 sq ft colonial in Massachusetts
Heat pump, city water, sump pump, home office
Heat pump (6,000W starting) + sump pump (2,150W) + office (300W) + lights (500W) = 8,950W
3,500 sq ft two-story in Florida
Two 3-ton AC units, pool pump, electric range
2x AC (9,000W starting) + pool pump (2,500W) + range (3,000W) + general (2,000W) = 16,500W
Pro Tips for Accurate Sizing
Don't forget the surge
Multiple motors can start simultaneously. Size your generator so that even the worst-case startup scenario stays under 80% of capacity.
Check your electrical panel
Your main breaker rating (100A, 200A, etc.) sets an upper limit. A 200A panel at 240V can draw up to 48kW, but you rarely use full capacity.
Consider future needs
Planning an EV? Adding a pool? Hot tub? Size for where you'll be in 5 years, not just today. Upgrading generators later is expensive.
Get a load calculation
A qualified electrician can perform a formal load calculation for your home. This costs $100-300 but ensures accurate sizing.
Frequently Asked Questions
Why does starting wattage matter?▼
Motors in appliances like AC units, pumps, and refrigerators need 2-3x more power to start than to run. Your generator must handle this surge. We recommend sizing based on the highest starting load you'll encounter.
Can I size based on square footage alone?▼
Square footage gives a rough estimate, but your actual needs depend on your specific appliances, especially AC size and whether you have electric vs gas appliances. A 2,000 sq ft home with all-electric appliances needs much more capacity than one with gas heating and water.
What happens if I get a generator that's too small?▼
An undersized generator will overload and shut down when you exceed its capacity. This can happen suddenly when a motor kicks on (like your AC compressor). It's frustrating and can damage both the generator and your appliances.
Is it bad to oversize my generator?▼
Moderate oversizing (10-20%) is actually recommended for headroom. However, significantly oversizing wastes money on purchase, uses more fuel, and can cause 'wet stacking' in diesel units. The ideal is 70-80% of capacity during peak loads.
How do I know my AC tonnage?▼
Check the data plate on your outdoor AC unit. The model number often contains the tonnage: '24' = 2 tons, '36' = 3 tons, '48' = 4 tons, '60' = 5 tons (these refer to BTUs in thousands). You can also find this on your HVAC invoice or home inspection report.
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