How to Choose Generator Fuel Type
Gasoline, propane, diesel, or dual-fuel — compare runtime, storage, and availability.
Read the guide →Generator Size Calculator
Find the right generator wattage to keep your essential appliances running during power outages.
Select Your Appliances
Enter how many of each appliance you want to run. Results update automatically.
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How This Calculator Works
This generator sizing calculator estimates the minimum generator wattage you need based on the appliances you want to run during a power outage.
How it works:
- Running watts: The continuous power each appliance needs to stay on. A refrigerator draws ~700W, a sump pump ~800W, a well pump ~1,000W. These add together.
- Starting surge: Motors (pumps, AC compressors, refrigerators) draw extra power for a few seconds on startup — typically 1,000-2,000W above their running wattage. The calculator adds the largest single surge to the total running load. This assumes the largest motor starts while other equipment is already running.
- Recommended size: The calculator suggests the next commercially available generator size above your total. Most portable generators come in 2,200W, 3,500W, 5,000W, 7,500W, 9,500W, and 12,000W sizes.
Example: Running a refrigerator (700W), furnace fan (800W), and a few lights (300W) totals ~1,800 running watts. A well pump adds 1,000 running (plus a ~2,000W startup surge). Running total: 2,800W. Largest surge: ~2,000W. Estimated peak: 4,800W + 10% safety margin → you need at least a 5,000W generator. See our generator fuel types guide for fuel consumption estimates at different load levels.
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Generator Transfer Switch vs. Interlock Kit
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Compare options →Essential Generator Maintenance Checklist
Seasonal maintenance tasks that keep your generator ready for the next outage.
View checklist →⚠ Important safety warning: Portable generators must be operated outdoors only — at least 20 feet from any building, with the exhaust directed away from doors, windows, and vents. Never operate a generator inside a home, garage, shed, basement, crawlspace, or partially enclosed area — even with ventilation. Carbon monoxide from generator exhaust is odorless and can be fatal within minutes. Use a working CO alarm in your home whenever a generator is running nearby.