Generator Size Checks
Will a 12000 watt generator run garage door opener, sump pump, and lights?
Use the default WattSizer rule: add running watts, then model the largest startup load while the other selected loads are already running.
A 12,000 W unit clears this estimate, subject to nameplate checks.
The peak-starting assumption is driven by Garage door opener. With the default 20% buffer, WattSizer rounds up to the next 100 watts.
| Appliance | Running | Starting | Source note |
|---|---|---|---|
| Garage door opener | 600 W | 1,800 W | Motorized openers have short startup peaks; default reflects common residential opener nameplates. |
| 1/3 hp sump pump | 800 W | 1,800 W | Pump manufacturer nameplates commonly show high locked-rotor starting demand; default is conservative for a 1/3 hp sump pump. |
| Ten LED lights | 100 W | 100 W | LED bulb wattage is printed on each bulb; default assumes ten mixed fixtures at about 10 watts each. |
Try the load yourself
Edit this scenario
| Load | Running watts | Starting watts |
|---|---|---|
Power station estimate
For battery units, the selected running load needs about 0 Wh for 8 hours or 0 Wh for 12 hours before weather, battery age, and inverter losses.
Safety check
Never operate a fuel-burning generator indoors, in a garage, on a porch, or near open windows. Use a listed transfer switch or interlock installed by a qualified electrician for home wiring, and verify actual device nameplates before buying equipment.
Generator or power station?
Fuel generators are useful for motor loads and longer outages, while battery power stations are better for indoor-safe electronics and medical-device planning. For battery sizing, this selected running load is about 14,400 Wh for 8 hours with the same buffer.
Never operate a fuel-burning generator indoors, in a garage, on a porch, or near open windows. Use a listed transfer switch or interlock installed by a qualified electrician for home wiring, and verify actual device nameplates before buying equipment.