Dual fuel
A dual-fuel generator runs on either gasoline or propane, switched by a selector and a regulator. Propane stores indefinitely and stays available when storms close gas stations, at the cost of roughly 10% less output than the gasoline rating.
Propane’s lower energy density per unit of fuel-air mixture is why the derating exists — a generator rated 7,500 W on gasoline typically delivers about 6,750 W on propane. Size against the propane figure if propane is your emergency plan.
Propane also burns cleaner (no carburetor gumming from stale fuel), which matters for a machine that may sit unused for a year between outages. The standard 20 lb grill cylinder holds about 4.6 gallons of propane and runs a mid-size generator for roughly half a day at moderate load.