What size generator do I need?
Running watts: Power needed for continuous operation.
Starting/surge watts: Extra power needed to start motors (2-3× running watts for motors).
Safety margin: Always size 20-25% above calculated need. Never run at 100% capacity continuously.
Determine what size generator you need for your home or project. Select your appliances and equipment to calculate the total wattage requirement, including startup surge watts. Get a recommended generator size with safety margin.
Generators are rated in watts. Running watts is the continuous power output, while starting (surge) watts handles the brief power spike when motors start up (typically 2-3 times running watts). Your generator must handle both the total running watts of all appliances AND the surge watts of the largest motor starting up simultaneously.
Refrigerator: 100-400W running, 1200W starting. Central AC: 2000-5000W running, up to 7500W starting. Sump pump: 800-1000W running, 1300-2500W starting. Well pump: 1000-2000W running, 2000-4000W starting. Microwave: 1000-1500W. Lights: 60-600W total. Space heater: 1500W. TV: 100-400W.
Portable generators (3,000-12,000W) cost $500-$3,000 and run on gasoline. Ideal for emergencies and specific circuits. Standby generators (10,000-48,000W) cost $3,000-$15,000 installed, run on natural gas or propane, and start automatically during outages. For whole-house backup, a standby unit is recommended.
NEVER run a generator indoors, in a garage, or near windows. Generators produce deadly carbon monoxide gas. Place generators at least 20 feet from your home with the exhaust pointing away. Use a transfer switch to safely connect to your home electrical panel. Never plug a generator directly into a wall outlet.
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