House Generator Calculator

House Generator Sizing Calculator

sq ft
Select how much of the home/load you want to power during an outage.

Calculating generator size…

Recommended Generator Size

Estimated Wattage Needed: 0 W
Generator Size Recommendation: 0 kW
Generator Type:
Tip: Always consult a licensed electrician for exact sizing. Add 20% margin for safety and future loads.

Choosing the right generator for your home is essential to keeping your household safe and comfortable during a power outage. If you pick a generator that’s too small, it won’t support your essential appliances. Choose one that’s too large, and you’ll spend far more than necessary on equipment and fuel.

The House Generator Sizing Calculator is designed to make this process quick and accurate. By entering details like your home’s square footage, number of bedrooms, and appliances you want to power, you can instantly get a reliable estimate of the generator size you need.

This tool not only suggests the wattage but also recommends whether you should go with a portable generator or a standby generator, ensuring you make an informed decision.

How to Use the House Generator Sizing Calculator

Using the calculator is simple and takes less than two minutes. Here’s a step-by-step guide:

  1. Enter Your Home’s Square Footage
    • Type the total square footage of your house (e.g., 2000 sq ft).
    • This helps estimate the load for a whole-house generator.
  2. Input the Number of Bedrooms
    • Add the number of bedrooms in your home.
    • Homes with more than three bedrooms typically require additional wattage.
  3. Select Essential Appliances
    • Choose from options:
      • Minimal: Lights, fridge, phone.
      • Average: Minimal + microwave, TV, computers.
      • High: Average + AC, washer/dryer, furnace, sump pump.
      • Whole House: Powers everything as normal.
  4. Specify if You Have Central Air Conditioning
    • Select Yes if your home uses central AC, as this adds significant wattage.
  5. Choose Preferred Generator Type
    • Options include Portable, Standby, or No Preference.
    • The calculator will still make a suggestion if you’re unsure.
  6. Click “Calculate”
    • The tool processes your inputs, displays a progress bar, and then shows your results.
  7. Review Results
    • You’ll see:
      • Estimated Wattage Needed
      • Recommended Generator Size (kW)
      • Suggested Generator Type
  8. Copy or Share Results
    • Use the “Copy Results” button to save them to your clipboard.
    • Or, click “Share Results” to send them directly via your device.

Practical Example

Let’s say you own a 2,000 sq ft house with 3 bedrooms, and you want to power an average set of appliances including lights, refrigerator, microwave, and TV. You also have central AC and no strong preference for generator type.

Here’s what the calculator might recommend:

  • Estimated Wattage Needed: 10,800 W
  • Recommended Generator Size: 11.0 kW
  • Generator Type: Standby

This makes sense because powering AC along with multiple appliances requires a larger generator, and standby units are ideal for whole-house coverage.

Features and Benefits of the Calculator

  • Quick & Accurate Estimates – Saves hours of manual research.
  • Customizable Inputs – Adjusts for home size, bedrooms, and appliances.
  • Considers AC Load – Accurately accounts for central air conditioning usage.
  • Safety Margin Built-In – Adds 20% overhead for unexpected surges.
  • Clear Recommendations – Provides exact wattage, kW, and generator type.
  • User Friendly – Simple, step-by-step process anyone can follow.
  • Copy & Share Options – Easily save or share your results.

Tips for Using the Calculator Effectively

  • Always round up your square footage rather than underestimating.
  • Select Whole House if you want to avoid constantly managing loads.
  • If your home has multiple large appliances (e.g., sump pump, furnace, washer/dryer), choose the High load option.
  • Consult a licensed electrician to confirm your results before purchase.
  • Consider fuel type (gasoline, propane, or natural gas) when choosing a generator model.

Common Use Cases

  • Homeowners preparing for outages caused by storms, hurricanes, or wildfires.
  • Real estate buyers estimating backup power needs for a new house.
  • DIY enthusiasts planning energy setups for cabins or vacation homes.
  • Families wanting peace of mind during grid instability.

Frequently Asked Questions (FAQ)

1. What does the House Generator Sizing Calculator do?

It estimates the correct generator size for your home based on square footage, bedrooms, and appliance load.

2. Why do I need to enter square footage?

Square footage helps determine total power needs, especially for whole-house coverage.

3. Does the number of bedrooms affect generator size?

Yes, more bedrooms often mean more lights, outlets, and appliances, requiring extra wattage.

4. What’s included in the “Minimal” appliance load option?

Lights, refrigerator, and charging devices like phones.

5. What does the “Average” option cover?

Minimal load plus a microwave, TVs, and computers.

6. What’s in the “High” load selection?

Average load plus large appliances like AC, washer/dryer, sump pump, and furnace.

7. How does “Whole House” differ?

It powers everything as if there were no outage, requiring the largest generator.

8. Why does the calculator ask about central AC?

Central air conditioners use a large amount of power, significantly affecting generator size.

9. What’s the difference between portable and standby generators?

Portable generators are smaller, movable, and usually run on gasoline. Standby generators are permanently installed and automatically turn on during outages.

10. How is the wattage calculated?

It uses appliance load estimates, adds AC if selected, adjusts for bedrooms, and includes a 20% safety margin.

11. Why add a 20% safety margin?

To handle unexpected surges and future increases in power demand.

12. Can I use this calculator for apartments?

Yes, but it’s most accurate for houses. For apartments, select smaller square footage and appropriate load.

13. Do I still need an electrician?

Yes. This tool gives an estimate, but a licensed electrician should confirm final sizing.

14. What size generator is common for most homes?

Many average homes fall in the 7–12 kW range, depending on appliances and AC.

15. How do I know if I need a standby generator?

If you want whole-house coverage or if your calculated size exceeds 9 kW, standby is recommended.

16. Can I run my central AC with a portable generator?

Usually no. Most portable units don’t provide enough power for central AC.

17. What happens if I buy a generator that’s too small?

It may overload, trip breakers, or fail to run all your essentials.

18. Is bigger always better?

Not necessarily. Larger generators cost more upfront and use more fuel.

19. Can I share the calculator results with my electrician?

Yes, you can copy or share results directly from the tool.

20. Is this calculator free to use?

Yes, it’s completely free and available online anytime.

Conclusion

The House Generator Sizing Calculator takes the guesswork out of choosing the right generator for your home. With just a few inputs, you can determine the wattage, recommended kW, and ideal generator type for your situation. Whether you’re preparing for hurricane season, frequent blackouts, or simply want peace of mind, this tool ensures you make a confident, informed decision.