Selecting the Best Fuel Option

Diesel, Natural Gas, Dual-Fuel, Bi-Fuel ... How Do I Choose?

Diesel generators are the established standard for power generators, however several options are emerging to address issues such as smart grids, grid reliability, and environmental regulations. Fuel prices, supply, and maintenance are key factors in lifecycle costs and reliability for power generation.

Several factors favor the use of gaseous fuels :

  • Relative fuel prices between 15 ppm ultra-low sulfur diesel and natural gas widening
  • Forecasts of domestic natural gas availability extremely robust
  • Energy and environmental policies now incorporate Full Fuel Cycle analysis, bolstering gaseous fuels
  • Lifecycle costs for gaseous generating sets are improving, including power density (first cost), fuel economy and maintenance costs

While these gaseous fuel options are not viable for Critical Operations Power Systems (NFPA 70 Article 708), natural gas, dual-fuel or bi-fuel generator equipment can provide advantages in reliability and lifecycle costs for many backup power applications.

Compare Fuel Types



Pipeline provides weeks to months operation On-site supply limited to 2 - 3 days Extends supply using natural gas; still limited by on-site storage

Cost Savings

Historically low natural gas prices; forecasts of domestic natural gas supply extremely robust Fuel costs for 15 ppm ultra-low sulfur diesel higher relative to natural gas
Added costs for fuel replacement; 1-year storage life
Added infrastructure (storage tank, spill containment, etc.)
Lower fuel costs than 100% diesel
Added costs for fuel replacement; 1-year storage life
Added infrastructure (storage tank, spill containment, etc.)


Proven reliability and performance Proven reliability and performance No change to power rating with similar cycle efficiency as diesel


Lower NOx, CO2 and particulates than diesel Higher NOx, CO2 and particulate emissions Significant decrease in PM emissions; lower CO2 emissions than diesel

Safety Concerns

None On-site storage presents moderate safety issues Improves on-site diesel storage, still presents a moderate issue

An Upward Trend for Choosing Natural Gas: More AHJ’s are recognizing natural gas generators for off-site fuel choice
Natural gas has been gaining popularity across a range of industrial applications due to influencing factors such as its stability and reliability, its cost effectiveness, its clean burning nature, and its resilient infrastructure. Read more »

More Information

Codes & Standards

Codes & Standards

When designing generator systems, engineers must ensure that the generators and the building electrical systems they support are appropriate for the application.
Explore Codes & Standards
Total Cost of Ownership

Total Cost of Ownership

Generac has made a fully customizable total cost of ownership tool to perform your own customized analysis for your unique situation.
Calculate Total Cost of Ownership
AGA Playbook

AGA Playbook

AGA published a report in 2017 examining the diversity within the commercial segment of the natural gas market to shed light on the range of customers, technologies, and end-uses that serve this important backbone of the U.S. economy.
View the AGA Playbook

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