Generators come in many shapes and sizes, utilizing a variety of fuel sources in order to operate. When deciding on what type of generator you should purchase for your facility, it’s important to understand the distinguishing attributes of your fuel options, as each power source is characterized by its own advantages – and a few disadvantages, too. To give you a better handle on which kind meets your specific needs, here we break down five prominent generator fuel types, as well as the pros and cons for each.
Diesel. Far and away, diesel is the most commonly used fuel for commercial and industrial backup generator sets – and has been considered the most reliable choice for years. Its capital cost advantage and the unwavering perception that other energy sources are not as effective in situations requiring backup power have rendered diesel the traditional top dog among various generator fuel types.
- Pros: Why are diesel gensets so popular? For one, diesel-powered generators often run more efficiently and, as a result, are generally less expensive to operate – particularly for generators that produce 150+ kW of power. Diesel is also an easy fuel to obtain, and the engine mechanisms running the respective generators are fairly straightforward. Most importantly, many mission critical facilities utilize this fuel type as a matter of compliance because code requirements call for fuel to be stored on-site.
- Cons: With that said, as diesel fuel is usually kept on-site, the added costs of managing its storage and maintenance may offset the otherwise beneficial cost differential. Without additives, its shelf life is only about 18-24 months, and its performance is less than ideal in frigid climates. However, its heavy carbon footprint is quite possibly the biggest detractor. As stricter regulations and tier standards are established across the globe in support of green initiatives, its negative impact on the environment has become increasingly problematic.
Bio-diesel. Bio-diesel is essentially a cleaner-burning replacement for diesel fuel that’s made from natural, renewable sources such as recycled vegetable oils and animal fats. Similar to its petroleum counterparts, bio-diesel operates in compression-ignition engines – and blends of up to 20% bio-diesel (in combination with petroleum diesel) are still compatible with the majority of diesel-powered equipment.
- Pros: Low level blends of up to 20% bio-diesel typically do not require any engine modifications at all, while providing the same payload capacity as 100% petroleum diesel. Bio-diesel use in a conventional diesel engine also notably reduces carbon dioxide emissions. On its own, this easily obtainable fuel source (due, in part, to the worldwide surplus of soybeans) isn’t as flammable as other choices, making it safer for storage, as well. Plus, the lubricating property of biodiesel may lengthen the life span of the engines it helps run.
- Cons: There are a few characteristics that make using bio-diesel a little more complicated than expected. Mixing and maintaining the proper percentage of oils and fuel is critical in order to maximize efficiency, and at present, bio-diesel is about 150% more expensive than petroleum diesel. Installing large storage tanks increases the cost of the system, and the distribution infrastructure of bio-diesel could also use some significant improvements.
- Pros: Gasoline is considered the simplest fuel to acquire, as a quick drive to the gas station is a common occurrence for most people. Moreover, there are many wallet-friendly gasoline generators on the market today. As other fuel types are more efficient and produce more power, cost is the biggest differentiator for this option.
- Cons: Gasoline is highly flammable, which makes storing a large supply relatively hazardous. Moreover, the shelf life of this fuel is only about twelve months, and like diesel, it’s a less effective generator fuel type for exceedingly cold weather conditions. However, as gasoline generators tend to run hotter in comparison to diesel generators, this incurs more wear and tear on the generator parts.
Natural gas. As legal regulations, technology and fuel pricing has changed over time, natural gas generators have won greater popularity in recent years. These days, they’re quite common for hospitals, schools, homes, and small businesses. Though a natural gas generator will use more fuel than one powered by diesel, this resource is plentiful and works well in very cold climates.
- Pros: As long as your generator is connected to the local utility grid, you don’t need to store your natural gas fuel on-site and re-fueling is a non-issue. A longer running generator fuel type, natural gas is also recommended for frigid areas, as it performs well in the cold. With the exception of earthquake prone regions, due to its availability, it is an optimal selection for locations that are likely to experience natural disasters, as the distribution infrastructure is laid underground. Of course, natural gas also emits fewer nitrogen oxides and particulate matter than diesel – and spillage and other environmental concerns are practically non-existent.
- Cons: While rare, breaks in the natural gas pipeline can be very dangerous. The most apparent sign of a natural gas line leak is that familiar rotten egg odor, which is added to the natural gas so it can be detected in such an occurrence. The most drastic hazard would be an explosion – yet again, this is a rare event. The other main disadvantages would include higher installation and initial costs and a lack of fuel availability in certain geographic areas.
Propane. Though it is not commonly used for large commercial or industrial applications, propane is a completely viable option for smaller gensets. Propane generators are often used to power a number of small applications during a power outage or to provide supplementary power to larger applications at any given time.
- Pros: Propane is a clean-burning gaseous fuel that basically has an indefinite shelf life. Furthermore, propane generators are characterized by a quieter engine noise, which is a great benefit in residential areas.
- Cons: Since the engine and fuel systems of propane generators are more complex relative to other power sources, installation and maintenance costs are driven upwards. Despite the seemingly limitless shelf life of propane, these types of generators also have a higher fuel consumption rate than diesel generators and they tend not to last as long.
Lastly, it’s important to note bi-fuel generator options are available in many cases. Though this isn’t a fuel “type” per se, generators that run on both diesel and natural gas are also becoming more and more common – and may help optimize performance, especially if you’re using the generator as a primary source of power.
The development of bi-fuel generators combines positives from two fuel types: most importantly, the capital cost benefits and power generation capabilities of diesel with the longer running times of natural gas. Your average bi-fuel generator will operate at a ratio of 25% diesel and 75% natural gas, with no reduction in power. Though more expensive, using these generators results in lower emissions, a lengthened runtime, and the ability to use smaller and less expensive fuel tanks.
Which fuel makes sense for you? It’s important to take the time to learn about your generator fuel choices and make sure that you select the optimal solution for your facility. You should ask yourself:
- How much power do you need?
- What is the on-site storage capacity?
- How will the fuel be delivered to your location?
- And can you access the fuel during an emergency situation?
Once you learn about the various options, it’s recommended that you consult your local Authorities Having Jurisdiction (AHJs) to familiarize yourself with the policies regarding using particular fuels in your specific situation. You can always reach out to local fuel providers and find out what is readily available to meet the needs of your project.
Sources: Gen-Tech, Inc., Critical Power Exchange, Generac, and Berkeley Biodiesel.
