Generator Fuel: Choosing between Diesel and Natural Gas

Generator Fuel: Choosing between Diesel and Natural Gas

Posted in: Diesel Generators Engine & Drivetrain Performance Power Outages

Nearly all Generators use either gasoline, diesel, natural gas or propane. In this post we are focusing on Diesel and Natural Gas and the pros and cons of buying an unit running on each type.

Diesel Advantages:

  • Least flammable fuel source
  • Fuel easily obtained (fuel is easier to obtain during a disaster because it is a necessary fuel for the military, trucking industry, and farming operations)
  • On site fuel delivery available
  • Less expensive to operate. The general rule of thumb for fuel consumption is 7% of the rated generator output (Example: 20 kW x 7% = 1.4 gallon per hour at full load).
  • Engines designed to work under a load for long periods of time and perform better when worked hard rather than operated under light loads.
  • Can operate in sub-artic conditions with fuel additive.
  • Equipment is competitively priced for a comparative sized water-cooled gaseous models with the same features.
  • In high use situations overall long term cost of operation is much lower than gaseous generators

Diesel Disadvantages:

  • Installing large storage tanks raises cost of system
  • May not be available during power outages.
  • Diesel fuel storage must be considered relative to required run time in your geographical area. If you live in hurricane country you might need a large fuel tank due to the high possibility of extended power outages
  • Engine noise is higher on a diesel compared to a gaseous engine. Use of a properly designed enclosure and sound attenuation system is more critical on a diesel engine system.
  • Requires clean moisture free fuel and a bit more maintenance than a comparable gaseous unit;
  • Some cities and counties require the generator on-board fuel tanks to be double-wall containment type which can increase the cost of the generator system.
  • Typically heavier and require more planning to load and unload than a lightweight gaseous generator set.

Natural Gas Advantages:

  • Unlimited fuel source – refueling not necessary
  • Clean burning
  • More available during power outage.
  • Quieter engine noise level
  • More emission compliant
  • More convenient fuel source (natural gas)
  • Gaseous engines do not have a problem with “wet stacking like diesels
  • less expensive units with air-cooled engines are budget priced.

Natural Gas Disadvantages:

  • May be unavailable during natural disasters (earthquakes, etc)
  • Lower power output (30% less BTU’s per unit than gasoline).
  • Fuel system plumbing results in higher installation cost.
  • Fuel not available in many areas.  
  • Natural gas (NG) begins to derate at +20 degrees above zero.
  • Initial cost of generator is somewhat higher, 15 to 20% especially in sizes larger than 30 kW.
  • More expensive to operate by as much as 3-times the fuel consumption compared to diesels;
  • Shorter life expectancy by a factor or 10 to 1 for air-cooled models and 3 to 1 for water-cooled models compared to diesel powered generator sets.
  • Smaller air-cooled gaseous engines are less expensive than comparable dieselsbut have a short life expectancy as low as 500-hours depending on engine make and use.
  • Hurricanes and earthquakes can disrupt the flow of natural gas lines with up-rooted trees
  • Natural Gas can become very dangerous if lines are broken.

At the time of choosing an unit, whether is Natural Gas or Diesel, the most important thing is to keep in mind the application and location of the generator and select the safest and more cost effective unit for your unique needs.