Pick the fuel for how you will run the machine during a real outage, not for a national cost-per-kWh claim we will not invent. Gasoline portable generators are widely available and easy to move; gasoline goes stale, is a fire hazard to store in quantity, and is often the first thing gas stations cannot pump when the power is out. Propane (LP) stores longer in a tank or in cylinders and is a common dual-fuel or tri-fuel option; you have to have enough tank capacity and a listed regulator and hose. Natural gas is the usual fuel for a standby generator that should start without someone hauling cans, provided the gas utility is still up and the meter and piping were sized for the load.
r/Generator threads spend as much time on this as on watts, for good reason. A manual portable on gasoline or propane still needs a person, an interlock or transfer switch, and outdoor placement. A natural-gas standby unit still needs an automatic transfer switch, a permit, and a load list. Dual-fuel portables trade some gasoline convenience for propane storage; they do not change the electrical hookup rules.
Size the electrical load first with the calculator, then talk to the installer or the supplier about fuel, runtime, and local codes. Never run any of these fuels indoors or in a garage.
This is not a permit calculation, a utility approval, or a substitute for a licensed electrician, HVAC contractor, or the authority having jurisdiction. Panel Headroom is an independent educational site. It is not a utility, a certification body, or a contractor. Electrical and generator work that is done incorrectly can cause fire, shock, or carbon monoxide poisoning. Use the adopted electrical code and manufacturer instructions; pull permits where required.