Home Generator Sizing Calculator
Determine the recommended size of a standby generator by combining your running load, the largest startup surge, and a safety margin. Enter wattages for essential circuits and choose a buffer percentage.
CalcSimpler Examples
- Running 4,500 W, starting 6,000 W, buffer 20% ⇒ 7,200.00 watts
- Running 3,200 W, starting 4,800 W, buffer 25% ⇒ 6,000.00 watts
FAQ
Why use the higher of running or starting watts?
Generators must handle the peak load, so the largest starting watt requirement drives the recommendation.
What buffer percentage should I choose?
20–25% is common to cover voltage drop, future loads, and high startup surges.
Does this include transfer switch losses?
Losses are minimal but you can increase the buffer if your switch or wiring introduces additional load.
Additional Information
- Recommendation = max(running watts, starting watts) × (1 + buffer%).
- Check appliance nameplates or manuals for accurate starting watt values.
CalcSimpler