Los Angeles, CA ― (May 22, 2015) ― The most basic difference between generators is the fuel that is used to power the units. In present times, when it comes to making choices regarding fuel, the most important factor is price. With the constantly increasing demand and steadily decreasing supply, fuel choice has become the most debated topic in almost every sphere. The key is to find a fuel that is cost effective and energy efficient while meeting your specific needs.

Traditionally, the viewpoint has been that diesel generators provide response, power, and longevity, while natural gas engines are more environmentally friendly. However, diesel is no longer the clear winner in terms of power and response. Natural gas industrial engine manufacturers can now optimize the RPM of these engines to make their response similar to that of diesel. Manufacturers are also producing natural gas units that can meet the 10-second startup requirement for backup systems that is traditionally associated with diesel engines, alone.

Comparing Costs:  It’s a common misconception that industrial diesel engines are considerably less expensive than comparable natural gas models. While the initial cost of large industrial natural gas generators may be higher than diesel, natural gas gensets of 150kW or below are actually more cost effective.

While the recent fall in natural gas prices is certainly making natural gas power equipment a more attractive option, plummeting oil prices are having a similar effect on diesel generator fuel.

Continuous Use: Diesel engines have a sweet spot of 50-70% of load, with 80% being the recommended maximum for long-term prime operation. Running them under a lighter load for long periods of time results in ‘wet stacking’, a condition that sends unburned fuel and soot into the exhaust system. The use of a load bank to consume the excess energy reduces ‘wet stacking’ but can waste a considerable amount of fuel.

As an alternative, those operators could instead choose a natural-gas-powered generator, which burn hotter than diesel engines. These engines are less likely to experience problems with unburned fuel, even if they are run at a lighter-than-optimal load. A key benefit to natural gas fuel is its capacity for long running time, and because natural gas is supplied by a Utility, refueling is not an issue.

Generator Life Span: Regarding longevity, diesel gensets still tend to have longer lives, on average, than natural gas generators. However, new technologies in natural gas engine manufacturing have increased engine resilience and longevity.

In short, companies that plan to keep their engines operating at peak condition will still likely get the greatest longevity from a diesel engine. However, extreme cases of ‘wet stacking’ can potentially cut a diesel engines life in half. For businesses that use generators only for backup power, a natural gas engine may provide nearly the same effective life, given how infrequently it is used.

Fuel Supply and Storage: Fuel handling is another area where diesel gensets and natural gas generators differentiate. As with other criteria, the benefits of one over the other often depend on the situation and need.

Natural gas is a mixture of hydrocarbons and is produced either from gas wells or in conjunction with crude oil. The liquid form is then transported to various areas where it is converted into its gaseous form. Thereafter, it is made available to people through pipelines and cylinders. This allows the generator to avoid fuel containment, spillage, and environmental concerns associated with diesel fuel storage.  And also allows a generator to run in a power outage or natural disaster that does not disrupt the earth. However, an event like an earthquake can damage pipelines, thus disrupting the fuel supply.

Diesel fuel is a mixture of hydrocarbons obtained by distillation of crude oil. Most diesel fuel is transported by pipeline from refineries and ports to terminals near major consuming areas, where it is then loaded into tanker trucks for delivery to retail service stations. A small amount of diesel fuel is transported by barge and rail.  Diesel fuel availability is limited only by delivery frequency and will only be impacted by weather if the generator is operating in a remote location and weather conditions make it impossible for fuel to be delivered. Additionally, diesel fuel can become contaminated with water, particulates and algae over time, however these problems can be prevented or mitigated with the use of additives.

Environmental Effects:  One of the big advantages of natural gas is that it burns more cleanly than diesel. Diesel’s environmental issues can be compounded by shortened engine life due to wet stacking, light loads, inadequate maintenance, and other common diesel generator issues—all of which can negatively impact emissions.  This can be a problem, not only for the environment, but also for regulatory compliance with the EPA and other agencies that protect it.

Engine maintenance and condition monitoring must be verified with EPA, and if operators allow engines to fall outside acceptable ranges with poor maintenance or fuel conditioning, steep fines can result. The fines for not keeping an engine in optimal running condition can obscure the added cost of a natural gas model. Consequently, businesses should consider all of these factors before they make an engine choice.

Conclusion: There are other minor factors to consider when comparing diesel generators to natural gas gensets, such as fire safety (advantage, diesel) and spill risk (advantage, natural gas).  Even here, manufacturers on both sides are taking steps to level the playing field. Diesel engine manufacturers are incorporating 110 percent spill containment catch basins into their enclosed generators, and natural gas generator manufacturers are making their enclosures more fire proof.

While each attempt to outshine the other, the diesel genset market still outpaces that of natural gas.  However, natural gas generator sales are now increasing to nearly 12 percent per year and sales of alternative energy options, such as biodiesel, are increasing, as well.

This battle, propelled with the continued improvements of these models on a near-monthly basis, ensures the contest between diesel and natural gas generators will be running for quite some time.