When the power goes out, your home doesn’t have to go dark. A whole-house standby generator can keep your lights, HVAC system, appliances, and even your internet running without interruption. But before you buy, there’s one essential question to answer: What size standby generator do I need for my entire home?
The short answer: Most homes require a standby generator between 14kW and 24kW to power everything during an outage. The exact size depends on your home’s square footage, the number of high-demand appliances, and your desired level of backup coverage.
In this guide, we’ll explain how standby generator sizing works, how to calculate your home’s total power needs, and how to choose the right generator to keep your home running smoothly during emergencies.
What Is a Standby Generator?
A standby generator is a permanently installed backup power system that automatically turns on during a power outage. Unlike portable generators, standby units are connected directly to your home’s electrical panel and run on natural gas or liquid propane.
Key features include:
- ✅ Automatic transfer switch (no manual startup required)
- ✅ Continuous power supply (can run for days or weeks)
- ✅ Whole-house coverage (depending on size)
- ✅ Weatherproof design for outdoor installation
With the right size generator, your household won’t skip a beat—even in extended blackouts caused by hurricanes, winter storms, or grid failures.
How Generator Size Is Measured
Generator size is measured in kilowatts (kW), which represent the amount of electrical power it can produce at one time.
- 1 kW = 1,000 watts
- Running Watts: Continuous output over time
- Surge Watts: Temporary boost to start appliances like ACs or refrigerators
Whole-house standby generators typically range from 10kW to 30kW+. Choosing the right size is essential to avoid system overload or underuse.
Step 1: Determine Your Home’s Electrical Load
The best way to size a generator is to calculate the total wattage of the appliances and systems you want to power. For whole-home coverage, this usually includes:
- Lights, fans, outlets
- Refrigerator and freezer
- HVAC system or electric furnace
- Water heater or well pump
- Stove, oven, microwave
- Dishwasher, washing machine, dryer
- Garage door, sump pump, security system
- Home office equipment, TVs, Wi-Fi router
Example Wattage Breakdown:
| Appliance/System | Running Watts |
|---|---|
| Central AC (3-ton) | 6,000W |
| Refrigerator | 600W |
| Electric Water Heater | 4,500W |
| Well Pump | 1,000W |
| Lights and Outlets | 1,000W |
| Oven and Stove | 5,000W |
| Washer & Dryer | 4,000W |
| Misc. Electronics | 1,000W |
Total estimated watts: ~23,100W = 23.1kW
Recommended generator size: 25kW or higher
🧠 Pro Tip: Consider a 15–20% buffer to account for starting surges and future power additions.
Step 2: Consider Your Fuel Type
Most standby generators run on either:
- Natural Gas: Continuous supply from municipal lines
- Propane (LP): Stored in tanks; requires regular refilling
Generator size affects fuel consumption rates. Larger generators burn more fuel per hour but may run more efficiently if not overloaded.
Average Fuel Consumption:
- 14kW: ~1.5–2.0 gal/hr (propane)
- 22kW: ~2.5–3.0 gal/hr (propane)
- 30kW: ~3.5–4.5 gal/hr (propane)
💡 Tip: If you’re on natural gas, you won’t need to worry about refueling. For propane, ensure your tank is large enough for multi-day outages.
Step 3: Decide on Whole-Home vs. Essential Load Coverage
If you want to power your entire home, you’ll need a generator that can support 100% of your load—typically 20kW or more for most households.
If budget is a concern, you might opt for “essential loads only”—just your fridge, sump pump, lights, and a few outlets. In this case, a 10–14kW generator might be sufficient.
Considerations:
- Do you want central air or just space heaters?
- Do you use electric cooking or have gas appliances?
- Will you need to run a well pump or electric vehicle charger?
👉 Recommendation: For true whole-house backup with comfort and convenience, choose a generator in the 20kW–26kW range.
Recommended Standby Generator Sizes by Home Type
| Home Size | Square Footage | Suggested Generator Size |
|---|---|---|
| Small home or cabin | Under 1,500 sq. ft. | 10kW – 14kW |
| Average suburban home | 1,500 – 2,500 sq. ft. | 16kW – 22kW |
| Large home with central AC | 2,500 – 4,000+ sq. ft. | 22kW – 26kW |
| Luxury or high-load home | 4,000+ sq. ft., pool, EV charger, etc. | 26kW – 38kW+ |
Best Whole-House Standby Generators (2024)
🛡️ Generac Guardian 24kW
- Smart grid integration with Wi-Fi monitoring
- Runs on natural gas or propane
- Best for large homes or whole-house coverage
🔋 Kohler 20RESCL 20kW
- High-quality build and fast transfer time
- Corrosion-proof enclosure
- Backs up large homes with ease
💨 Champion 14kW Home Standby
- Ideal for essential load or medium-sized homes
- Affordable yet powerful
- Quiet operation and easy maintenance
FAQs About Standby Generator Sizing
Q: Can a 22kW generator run my entire home?
Yes—for most average-sized homes. A 22kW generator can power lights, HVAC, appliances, and some high-demand systems during an outage.
Q: What happens if I get a generator that’s too small?
Undersized generators can overload, shut down, or fail to start all necessary appliances. It’s better to size slightly up than down.
Q: Should I use a load-shedding or smart management system?
Yes, especially for smaller generators. These systems prioritize appliances and prevent overloads—allowing you to run more with less.
Q: Can I install a standby generator myself?
No—professional installation is required for safety, code compliance, and warranty coverage. Always hire a licensed electrician or installer.
Q: How much does a standby generator cost?
Expect to pay $8,000–$15,000 for a full system, including the generator, transfer switch, installation, permits, and fuel connection.
Conclusion: Choose the Right Size for Total Peace of Mind
When choosing a standby generator for your entire home, size truly matters. An underpowered unit may leave you in the dark, while the right-sized system will provide seamless backup power through any outage.
For most homes, a generator in the 20kW–26kW range offers complete coverage, fuel efficiency, and reliable performance. Whether you’re planning for storms, blackouts, or long-term preparedness, the right generator gives you total control over your comfort and safety.
Need Help Picking a Generator?
Start with our expert guide: What Size Generator Do I Need for My Home? — designed to help you compare models, calculate loads, and find the perfect fit for your household.