Choosing the right generator size is essential for powering your home safely and efficiently during outages. Undersized generators may fail under load, while oversized ones waste fuel and money. The Generac Generator Calculator is a simple, intelligent tool designed to help homeowners determine the ideal generator size based on home size and selected appliances.
Generac Generator Calculator
How the Generac Generator Calculator Works
The calculator uses two main inputs:
- Home Size (in square feet):
Based on an industry-standard load factor of approximately 3 watts per square foot. - Selected Appliances:
Appliances like air conditioners, water heaters, and refrigerators are factored into the total load in watts.
The tool:
- Converts appliance wattage to kilowatts (kW).
- Adds base load from home size.
- Applies a 20% safety buffer to account for startup surges.
- Recommends the closest standard Generac generator size (8, 10, 14, 16, 20, 22, or 24 kW).
How to Use the Calculator
Step-by-Step Instructions:
- Enter your home’s size (in square feet).
- Check the appliances you plan to run during a power outage.
- Click “Calculate.”
- The recommended generator size (in kilowatts) will appear instantly.
- To clear inputs, click “Reset.”
Example Calculation
Scenario:
- Home size: 2,000 sq ft
- Selected appliances: Refrigerator, Air Conditioner, and Lights & Fans
Calculation:
- Base Load: 2,000 sq ft × 3 W = 6,000 W → 6 kW
- Appliance Load:
- Refrigerator: 1,000 W
- Air Conditioner: 3,500 W
- Lights & Fans: 800 W
- Total: 5,300 W → 5.3 kW
- Combined Load: 6 kW + 5.3 kW = 11.3 kW
- With 20% buffer: 11.3 × 1.2 = 13.56 kW
- Suggested Standard Generator Size: 14 kW
Benefits of Using This Calculator
- ✅ Fast & Accurate: Delivers results in seconds.
- ✅ User-Friendly Interface: Designed for all users.
- ✅ Realistic Estimations: Accounts for home size and appliance wattage.
- ✅ Matches Standard Sizes: Aligns results with available Generac models.
- ✅ No Guesswork: Avoids under- or overestimating power needs.
Appliances Included
| Appliance | Estimated Wattage |
|---|---|
| Refrigerator | 1,000 W |
| Air Conditioner | 3,500 W |
| Water Heater | 4,500 W |
| Lights & Fans | 800 W |
| Sump Pump | 1,300 W |
You can expand the calculator by adding more appliances based on your audience.
Who Should Use This Tool?
- Homeowners preparing for emergency power needs.
- Builders and contractors estimating backup generator requirements.
- Electricians advising clients on generator sizing.
- People living in hurricane-prone or outage-heavy areas.
Mobile & Desktop Friendly
The calculator is designed to work seamlessly on all devices — desktops, tablets, and smartphones. No app or plugin required.
Top 20 FAQs About the Generac Generator Calculator
1. What is a Generac Generator Calculator?
It’s a tool to estimate the size of the Generac generator needed to power your home based on square footage and appliances.
2. Is this calculator accurate?
Yes, it uses standard wattage values and a 20% safety margin for reliable recommendations.
3. How is generator size measured?
Generator capacity is measured in kilowatts (kW), where 1 kW = 1,000 watts.
4. Can I use this for commercial buildings?
It’s optimized for residential homes. For commercial use, consult an electrician.
5. Does home size really affect generator size?
Yes. The larger your home, the more lights, outlets, and HVAC power you’ll likely need.
6. What if I have solar panels?
This tool is for traditional backup generators. Solar panel systems require different calculations.
7. Can I add more appliances?
Yes, developers can extend the calculator to support additional items.
8. How do I know what wattage my appliances use?
You can find wattage ratings on the product labels or user manuals.
9. Does this include surge power?
Yes. The 20% buffer helps accommodate startup surges.
10. Is 3W per square foot a universal standard?
It’s a reliable estimate for typical homes, though actual usage may vary.
11. What if I check all the appliances?
The calculator will include the total wattage and suggest a suitable generator size accordingly.
12. Can I use this offline?
No, it’s an online calculator and needs an internet connection.
13. Is it free to use?
Yes, the calculator is completely free.
14. Is this endorsed by Generac?
No, it’s an independent tool that recommends sizes based on Generac’s standard options.
15. Do I need to enter exact wattages?
No, preset wattages are provided for ease. You may customize the script if needed.
16. What happens if I enter 0 sq ft?
The calculator will assume minimal base load and compute based only on appliance load.
17. What’s the max recommended size?
The calculator suggests up to 24 kW, the highest in the preset list. For more, consult an expert.
18. How is the standard generator size selected?
It picks the smallest standard size that is greater than or equal to your total load with buffer.
19. Can this be used for off-grid setups?
Yes, but it’s intended for general backup needs. Off-grid systems may need specialized planning.
20. Where can I buy a Generac generator?
Visit authorized Generac dealers, hardware stores, or the official Generac website.
Final Thoughts
Having the right generator size means peace of mind during power outages. The Generac Generator Calculator removes the guesswork and helps you make a confident choice, tailored to your needs.