It is quite common for Whole House Generators and some Portable Generators to support both Natural Gas and Liquid Propane as Fuel sources. However, the Generator must be specifically configured to accept either Natural Gas OR Liquid Propane as the fittings and pressures are different for each Fuel type.
If an option, usually the best Fuel choice for your Generator is Utility Supplied Natural Gas. It is delivered in pipes buried in the ground under high pressure. Delivery is based on pressure physics and not at all dependent on Electricity. Natural Gas is stored in huge tanks with floating tops at the Utility. As the Natural Gas in the tank is consumed by customers, the delicately balanced weight of the top of the tank lowers and forces the Natural Gas out of the tank and in to the Distribution pipes to your home. The Utility Gas Supply is rarely disrupted during even the worst storms specifically because the delivery system is not dependent on external electrical power and the pipes are mostly underground.
I have never lost my Natural Gas Service due to a Storm. Check with your local Natural Gas Utility for the history of outages in your area. For example, in the North Shore of Long Island, NY, Gas Service is virtually 100% reliable. But in parts of the South Shore of Long Island, due to an antiquated delivery system, every time severe flooding occurs, Gas Service is suspended.
The significant advantage of Natural Gas as a Fuel source for a Generator is that it is a continuous, 24/7 supply – provided that Gas Service has not been disrupted – which as stated for most areas is rare. Natural Gas is usually the least expensive of all Fuel Options.
The only significant disadvantage of Natural Gas is that it is not necessarily the most efficient of the Fuel sources. In my article, “Hurricane Tech – The Whole House Generator Option”, I discuss the efficiency differences between Liquid Propane and Natural Gas. However, the convenience and low cost of Natural Gas far outweigh the marginal loss in Generator efficiency. A minor issue is also the increased cost of initial installation. You may need Permits from your town and are usually required to use a Licensed Plumber. A Town Building Inspector will want to perform a Pressure Test to make sure the connection is at the proper specification.