Generator Size Calculator

Total your appliance wattage and factor in starting surge to find the perfect generator size.

Appliances & Devices
Custom Equipment
⚠️ Please enter a valid running wattage.
Recommended Generator
0
Watts (Minimum Size)
0 W Total Running
Load
0 W Highest Single
Start Surge
Power Load Breakdown
Running Watts: Base power to keep items on.
Starting Surge: Extra burst needed for the largest motor.
20% Safety Margin: Prevents overload & extends generator life.

Running Watts vs. Starting Watts

When sizing a generator, you must differentiate between two types of power loads:

  • Running (Rated) Watts: The continuous wattage an appliance needs to keep operating.
  • Starting (Surge) Watts: The extra power needed for 2–3 seconds to start a motor. This is common in refrigerators, air conditioners, and well pumps.

The Math: This calculator totals all your running watts and then adds only the highest single starting surge. It's highly unlikely all your motors will start at the exact same millisecond, but your generator must be able to handle the biggest surge while everything else is running. Finally, we add a 20% safety margin so you never run your generator at 100% maximum capacity.