Page last updated Oct 20, 2021 @ 10:06pm

Fuel Selection

There are several factors to consider when selecting the fuel for use with engine generator sets.  Use the comparison chart and information below for a rough guide.

 

Fuel Comparison Chart

FACTOR GASOLINE DIESEL NATURAL
GAS
VAPOR
PROPANE
LIQUID
PROPANE
ENGINE
COST
EXCELLENT
(many low-cost gensets on market)
VARIES
(higher cost in small sizes)
VARIES
(low cost in small sizes)
VARIES
(low cost in small sizes)
VARIES
(low cost in small sizes)
FUEL SYSTEM INSTALLATION & STORAGE COST VARIES
(low cost in small sizes)
VARIES
(low cost in small sizes)
EXCELLENT
(if gas service already available at site)
MEDIUM
(if adequately sized tank already at site)
MEDIUM
(if adequately sized tank already at site)
FIRE & PERSONNEL
SAFETY
POOR
(highly flammable, vapors poisonous)
EXCELLENT
(high flash point)
MEDIUM
(rare leak risk)
MEDIUM
(rare leak or tank explosion risk)
MEDIUM
(rare leak or tank explosion risk)
ENVIRONMENTAL
IMPACTS
POOR
(spill risk, exhaust not clean)
POOR
(spill risk, exhaust not clean)
EXCELLENT
(clean burning)
EXCELLENT
(clean burning)
EXCELLENT
(clean burning)
FUEL
AVAILABILITY
MEDIUM
(easy to purchase)
MEDIUM
(must be delivered & stored)
EXCELLENT
(storage not req'd, supply rarely lost)
MEDIUM
(must be delivered & stored
MEDIUM
(must be delivered & stored
COLD
STARTING & OPERATION
POOR
(forms gum deposits)
MEDIUM
(hard starting at cold temperatures)
EXCELLENT MEDIUM
(tank must be large and full for vaporization)
EXCELLENT
(no tank vaporization issue)
ENGINE
LIFE/WEAR
POOR/ MEDIUM
(depends on engine type)
EXCELLENT MEDIUM MEDIUM MEDIUM

 

Gaseous Fuels

Gaseous fuels such as natural gas, vapor propane and liquid propane are the most common choice for small automatic standby generators.  This is because the engines are economical to build, these fuels provide good starting reliability and they are in common use and available everywhere.  When purchasing a gaseous fueled genset you must remember the following:

 

Gasoline

The gum deposits that gasoline forms when it is stored can cause problems in fuel filters and carburetors, especially in cold weather and when the engine is not operated often enough.  There are gasoline additives that can reduce this problem, such as Stabil.

 

Diesel

Diesel fuel has traditionally been used in many automatic standby generator applications.  As long as the engine is kept warm when it is not running, starting reliability can be excellent.  However, there are now emissions limitations in some areas that make it difficult for a diesel permit to be approved.  There are also costs associated with fuel spill prevention and containment.

 

Fuel Energy Content & Conversions

Here are some approximate energy conversion factors.  The exact values will vary depending on the quality of the fuel and in some cases the pressure.  SCF and SCFH are abbreviations for standard cubic feet and standard cubic feet per hour.

Propane

1 gallon = 91,500 BTU
1 cubic foot = 2,500 BTU
1 pound = 21,500 BTU
4.24 lbs = 1 gallon
36.39 cubic feet = 1 gallon

Natural Gas

1 cubic foot = 1,050 BTU

Gasoline

1 pound = 19,000 BTU
1 gallon = 125,000 BTU
1 gallon = 6.1 lbs

Oils

1 gallon kerosene = 135,000 BTU
1 gallon #2 oil = 138,500 BTU
1 gallon diesel = 139,200 BTU
1 gallon #6 oil = 153,200 BTU

Other Fuels (dry)

1 lb hydrogen = 51,892 BTU with steam as product
1 lb coal (anthracite) = 12,700 BTU
1 lb coal (subbituminous) = 8,800 BTU
1 lb coal (bituminous) = 11,500 BTU
1 lb pine wood bark = 9,200 BTU
1 lb hardwood bark = 8,400 BTU
1 lb wood = 7,870 BTU
1 lb dung = 7,500 BTU
1 lb waste paper = 6,500 BTU
1 lb sawdust/shavings = 3,850 BTU
1 kWH electricity = 3,413 BTU
1 therm any fuel = 100,000 BTU

 

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