How to read the recommendation
Recommended running rating = your running total × 1.2, rounded up to the next 500 W. Recommended peak coverage = running total + largest starting surge, rounded up to the next 500 W. At 4,000 W running and a 1,500 W surge, that is 5,000 W running and 5,500 W peak.
The 20% margin keeps the engine off its continuous limit while compressors cycle. Actual demand varies with weather, appliance condition and what your household switches on; dual fuel models also rate lower on propane than on gasoline — plan around the rating of the fuel you will depend on.
Before choosing a generator
- List essential loads and read their nameplate running watts.
- Identify the largest motor-start surge (well pump, sump pump, AC).
- Check both figures against the exact listing and manual, per fuel.
This tool does not establish equipment safety or electrical compatibility. Do not use it to qualify backup power for medical or life-support equipment; follow the equipment provider's requirements and a qualified backup plan. Any connection to household wiring belongs to a licensed electrician.
Read our research methodology and the starting vs running watts guide.