When the power goes out, a portable generator can be a lifesaver—keeping your lights on, your food cold, and your home safe. But before investing in one, the most important question to ask is: What size portable generator do I need for my home’s emergency needs?
The right generator size depends on the total wattage of the appliances and systems you want to power. Too small, and you risk overloads or brownouts. Too large, and you may overspend on fuel and equipment you don’t need.
In this guide, we’ll walk you through how to calculate your emergency power needs, how to match that to a generator’s output rating, and what other features you should consider when shopping for the best portable generator for your home.
What Does “Generator Size” Really Mean?
When we talk about generator size, we’re referring to its power output capacity—measured in:
- Watts (W): The basic unit of power output. Tells you how many watts the generator can supply.
- Running Watts: The continuous power the generator can produce for extended periods.
- Starting (Surge) Watts: The higher burst of power required to start appliances with motors, like fridges or sump pumps.
Most portable generators range from 2,000 watts to 10,000 watts+ depending on their intended use.
Step 1: Determine What You Need to Power
First, make a list of the essential appliances and devices you want to power during an outage. The more you want to run, the bigger your generator must be.
Common Emergency Appliances and Their Wattage:
| Appliance | Running Watts | Starting Watts |
|---|---|---|
| Refrigerator (Energy Star) | 150W | 600W |
| Sump Pump (1/3 HP) | 800W | 1,500W |
| Microwave (1,000W) | 1,000W | 0W |
| Furnace Fan | 800W | 1,600W |
| Window AC (10,000 BTU) | 1,200W | 2,000W |
| LED Lights (5 bulbs) | 50W | 0W |
| Wi-Fi Router | 15W | 0W |
| Laptop | 60W | 0W |
🧠 TIP: Always factor in surge wattage for motor-driven appliances, which can spike 2–3x higher than running wattage.
Step 2: Calculate Total Wattage Requirements
Add up the running watts of everything you want to run simultaneously. Then, add the single highest surge wattage (not all surges happen at once).
Example Emergency Load:
- Fridge: 150W running / 600W surge
- Sump pump: 800W running / 1,500W surge
- Lights: 50W
- Wi-Fi router: 15W
- Phone charging: 10W
Total running watts: 150 + 800 + 50 + 15 + 10 = 1,025W
Minimum generator size needed: 1,025 + 1,500 = 2,525 watts
So a generator rated for at least 3,000W starting and 2,500W running would be ideal in this example.
Step 3: Match Your Needs to Generator Size Categories
⚡ 2,000 – 3,000 Watts: Basic Emergency Use
Good for running a refrigerator, lights, phones, router, and one or two small devices.
⚡ 3,000 – 5,000 Watts: Mid-Sized Emergency Coverage
Can handle a fridge, sump pump, lights, router, laptop, TV, microwave, or space heater—but not all at once.
⚡ 5,000 – 7,500 Watts: Full Essentials + Comfort
Can power multiple high-draw appliances like well pumps, AC units, or electric stove burners alongside smaller loads.
⚡ 8,000 – 10,000+ Watts: Whole-House Capable
Enough to run most of a home’s circuits with a transfer switch—ideal for larger families or high-load homes.
Do You Need to Power the Whole House?
A portable generator isn’t always meant to power your entire home. Instead, it’s often best used for:
- 🏠 Essential loads: fridge, lights, router, medical devices
- 🛠️ Critical systems: sump pump, furnace blower, well pump
- ⚠️ Safety and communication: phones, security systems, radio
If you need whole-home backup, consider a higher-wattage portable unit with a transfer switch—or explore standby generators instead.
Best Portable Generators for Emergency Home Use
🔥 Generac GP6500 COsense
- 6,500 running watts / 8,125 starting watts
- CO detection for safety
- Can power multiple circuits with a manual transfer switch
🔋 Bluetti AC200MAX (Solar-Compatible)
- 2,200W AC output / 4,800W surge
- 2,048Wh battery (expandable)
- Runs fridge, CPAP, lights, electronics quietly
💨 Honda EU3000iS
- 2,800 running watts / 3,000 starting watts
- Super quiet operation (50–57 dB)
- Ideal for smaller homes or apartments
Other Key Features to Consider
- 🎛️ Inverter Technology: For stable, clean power to run electronics safely
- 🔌 Outlets: Look for 120V, 240V, USB, and GFCI outlets
- 🛑 CO Safety Shutdown: Automatically shuts off if carbon monoxide is detected
- 🔊 Noise Level: Choose inverter models for quieter operation
- 🧳 Portability: Wheels and handles make transport easier
FAQs About Portable Generator Sizing for Home Emergencies
Q: Can I plug my generator directly into my house?
No. This is extremely dangerous and illegal in most areas. You must use a manual transfer switch installed by a licensed electrician to power home circuits safely.
Q: What size generator do I need to power a refrigerator and sump pump?
At minimum, a 3,000-watt generator is recommended to handle the combined surge and running loads safely.
Q: Can I use extension cords instead of a transfer switch?
Yes—for smaller setups. Plug appliances directly into the generator using heavy-duty, outdoor-rated extension cords. Don’t exceed rated amp loads.
Q: How do I calculate the exact size I need?
Use our wattage calculator above, add up all running watts, then add the highest surge wattage to find the right size.
Q: Is bigger always better?
Not necessarily. Larger generators use more fuel and cost more upfront. Get the right size for your actual emergency needs to maximize efficiency.
Conclusion: Choose the Right Generator Size for Peace of Mind
When it comes to emergency preparedness, the right portable generator size ensures you’re never left in the dark. By calculating your essential loads and understanding surge requirements, you can confidently choose a unit that will power your home safely and efficiently during any outage.
Whether you need to keep just the basics going—or want enough power to run the majority of your home—a properly sized generator gives you control, comfort, and security when the unexpected hits.
Need Help Picking the Right Generator?
Start with our in-depth guide: What Size Generator Do I Need for My Home? to compare fuel, wattage, features, and top-rated models.