Tri-fuel
A tri-fuel generator runs on gasoline, propane, or natural gas. The natural-gas option lets a portable unit draw unlimited fuel from the home’s gas meter — with the lowest output of the three fuels, typically about 20% below the gasoline rating.
Natural gas has the lowest energy density of the three fuels, hence the deeper derating; propane sits between at roughly 10% below gasoline. In exchange, a natural-gas quick-connect on the house line ends fuel logistics entirely for long outages.
The natural-gas hookup requires a plumber or gas fitter to install a properly sized quick-connect tee, and the meter must have capacity for the generator on top of the furnace and water heater.