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Internal combustion engines will run on just about anything. Some fuels, however, are inconvenient and hard to handle while others are reliable and easy to use. These are the five most common emergency generator fuels ranked in order of preference.
Diesel
Diesel is the best choice. It is readily available and
packs a lot of energy in each gallon – about 130,000 BTUs. This means you
get good fuel economy, and more run time per gallon. It also stores well
if you keep it clean.
LPG Liquid
LPG liquid is the next best fuel. It is impossible to
contaminate and keeps forever. But it requires special handling. Since
it may be difficult to get during an emergency, you should use a big tank.
It also contains lubricating oil that tends to collect in the fuel delivery
system on the engine and must be regularly drained.
LPG Vapor
LPG vapor is also an excellent emergency generator fuel.
It has the same qualities as LPG liquid without the lubricating oil problem
since it is vaporized in the tank. However, the tank may not be able to
naturally vaporize enough fuel for large units. LPG vapor should only be
considered for generators sized below 30 kW.
Natural Gas
Natural gas is good fuel where it is available. However,
it has a low heat value (about 1000 BTUs per cu ft) which may require the
engine be derated. It is subject to contamination and, since it is a public
utility, the supply may be interrupted.
Gasoline
Gasoline should never be used as an emergency generator
fuel. Without special attention it will gum up the fuel delivery system.
Its storage life is only a few months. After this, it becomes difficult
to burn in a standard engine. If the generator can be started it may not
be able to carry a load if it is trying to burn old gasoline.