Air Compressor Generator Calculator
Air compressors have massive starting surges. Calculate the generator size needed to reliably start and run your compressor without tripping breakers.
Compressor Specs
Standard portable compressors use Capacitor Start. Industrial units may have Soft Start.
Required Generator Size
Power Breakdown
How to Size a Generator for an Air Compressor
Check Motor HP
Look at the motor's data plate (not the tank sticker). Note the Horsepower (HP) rating.
Identify Start Type
Determine if it's Capacitor Start (common) or Hard Start. This greatly affects the required surge watts.
Calculate Surge
Use this calculator to find the starting watts. Generators must handle this peak to avoid stalling.
Why Compressors are Hard to Start
Air compressors are notorious for requiring large generators. The motor must start against the resistance of the compressor pump, often under pressure. This creates a "Locked Rotor" condition that demands 3 to 6 times the running wattage.
Troubleshooting Generator Problems
- Tripping Breakers? The starting surge is likely exceeding your generator's peak capacity.
- Stalling Engine? Use a thicker extension cord (10 or 12 AWG) to reduce voltage drop.
- Unloader Valve: Ensure your compressor's unloader valve is working. This releases tank pressure from the head, allowing the motor to spin freely for a second before pumping.
Recommended Gear
Essential equipment for running air compressors.
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