Generator Wattage Calculator
Add up appliance running and surge watts from an editable checklist to get a recommended generator size.
Processed locally in your browser — nothing is uploaded.
| Use | Appliance | Running W | Surge W | |
|---|---|---|---|---|
Results
- Total running watts
- 800 W
- Largest single surge premium
- 1,500 W
- Required capacity
- 2,300 W
- Recommended generator size
- 2,760 W
Motors draw far more at start-up; only one is assumed to start at a time.
Required capacity plus 20% headroom.
Default wattages are typical values — check each appliance's nameplate. Running a generator near its maximum continuously shortens its life; oversizing slightly is safer than undersizing.
About Generator Wattage Calculator
Tick the appliances you need to run at once — each row has editable running and surge watts with typical defaults. The recommendation adds all running watts plus the single largest surge premium (motors briefly draw several times their running power at start-up), then 20% headroom.
Common uses
- Size a portable generator for storm outages (fridge, sump pump, lights)
- Plan a job-site or camping generator around specific tools
- See how much adding a window AC changes the requirement
Example
Input
Fridge 700/2200 W + sump pump 800/2000 W + lights 100 W
Output
1,600 W running · 3,100 W required · ≈ 3,720 W recommended
Limitations
- Defaults are typical values — use each appliance's nameplate. Assumes only one motor starts at a time.