The Complete List of Generator Fuel Types

When it comes to backup generators for commercial or industrial applications, they are most commonly well-known and divided by their fuel types — diesel and natural gas. A lesser-known fact about commercial generators is that some generators accept fuel other than diesel or natural gas. There are even bi-fuel and tri-fuel generators that enable backup power supplies to run off multiple fuel types.

While each generator and correlated fuel type has its own advantages, there are a few quirks that ultimately sway a buyer’s decision when purchasing a generator. While there’s not necessarily a single best gas for generators, below is a list of generator fuel types available that may help you choose the best fuel type for your needs.


Gasoline is primarily used for portable residential generators, such as those sold at major hardware stores, because gasoline tends to have a shorter shelf life and flash-point temperature than some of its counterparts. This means it can ignite at lower temperatures when compared to diesel fuel, for example. While gasoline may work fine for residential generators that generally need to be refueled less often, it’s not commonly considered a viable fuel source for commercial and industrial applications.


Diesel generators run off their namesake — diesel fuel. Diesel generators are one of the most commonly used generators available on the market due to their build, versatility and durability, enabling this type of generator to fit various needs across multiple industries. Diesel generators can also be mounted to trailers to provide functional portability, which allows the user to haul the generator from site to site and different project locations, including off-site projects that have yet to be connected to the utility grid or disaster response and preparedness needs.

There are many benefits to diesel fuel for generators but also some downsides. Many diesel generators have a diesel fuel tank connected to them, meaning the fuel source is finite. When using a diesel generator as a backup power solution, it’s important to note that fuel may run out. You should set up protocols to replenish the diesel fuel source, whether that’s via diesel fuel deliveries or storage cubes that can be stored and relocated as needed.

While diesel fuel can be stored, it does need to be maintained to some degree, as diesel fuel can go bad. During inclement weather or natural disasters, diesel fuel deliveries may not be possible, so it’s critical to plan for additional fuel when considering a diesel generator as a backup power solution.

Diesel generators also produce emissions considered harmful to the environment. Diesel generators are classified by EPA tier ratings. When considering a diesel generator, check your state and local EPA tier requirements before purchasing. If you’re operating in California, you must also consider California Air Resources Board (CARB) regulations when purchasing a generator.

Natural Gas

Natural gas generators are also very popular. Natural gas is considered one of the cleanest burning fuel types, as it produces the fewest emissions out of all the fuel types available for backup generators. Natural gas generators are connected to the gas pipeline, which removes the need for fuel storage and enables the generator to run longer without needing fuel replenishment.

A downside to using a natural gas generator is that in natural disasters, emergencies or even routine maintenance, the natural gas utility is often one of the first things cut off. This is for safety precautions, as natural gas is extremely combustible. This process renders the natural gas generator inoperable.

Additionally, natural gas generators require more routine inspection, service and maintenance. This is because natural gas generators are spark-ignited and have spark plugs. Extra care must be taken to service, maintain and replace these plugs as necessary, as well as carefully inspect any tubes or hoses to prevent possible fires.


If you planned on using a natural gas generator as a backup power solution but are not connected to the main gas pipeline, a solution may still be available! Propane generators are natural gas generators that have been converted to accept and run off propane via a conversion kit. This enables users to purchase large propane tanks to store and connect propane to the generator during a power outage. In addition to its long shelf-life, propane enables flexibility for those using a natural gas generator and allows for fuel storage.

A downside is that propane is considered less efficient when compared to a diesel or gasoline generator. However, propane will not degrade compared to diesel or gasoline, making it an ideal solution for those who use their backup generators sporadically. Like natural gas, propane burns cleanly and releases fewer harmful emissions into the atmosphere when compared to other backup generator fuel options.

What Generator Fuel Is Best?

When determining which generator fuel type best fits your needs, it’s important to consider factors such as fuel availability and storage capabilities. A major factor added to the equation would be the generator size and the fuel requirements necessary to ensure it can run optimally.

Since each fuel type has its own advantages and disadvantages, the best fuel type for deciding on a backup generator depends heavily on your situation and needs. Consider the following factors to help determine which generator may be the best fit for your needs.

Shelf Life

Shelf life refers to how long fuel can be stored before beginning to degrade. This factor relates to how often you use your generator, as you want to avoid letting fuel go bad before you can use it. For example, when considering propane vs. diesel generator fuel shelf lives, both have relatively long shelf lives compared to gasoline.

However, diesel fuel can and will degrade much faster than propane. Diesel fuel treatments or services like diesel fuel polishing can help maintain and slow diesel fuel degradation, but ultimately the diesel fuel may need to be replaced.


Consider whether the fuel type can be stored and whether you have storage space. For example, diesel fuel is often stored in tanks that feed into the diesel generator, meaning the more diesel fuel available in the tank, the longer the diesel generator can operate.

Most types of generator fuel can be stored in somewhat similar ways, except for natural gas. While this is generally fine in applications where natural gas generators are used, if supply from the natural gas utility is cut off, the natural gas generator will be rendered inoperable.


Consider how you will replenish your fuel source. Your fuel supply can be delivered or obtained and transported to your facility, depending on the fuel type. Gasoline tanks for portable residential generators can be filled at your local gas station, while natural gas generators are connected to the natural gas pipeline. For fuel types such as diesel, you may require a company to deliver diesel fuel and refill your storage tank as needed.

In emergencies and inclement weather, receiving a diesel fuel delivery may prove difficult, so it’s important to consider contingency measures.


If you’re evaluating environmental perspectives when considering a backup generator, natural gas and propane tend to be favorable choices. As we mentioned earlier, these fuel types burn the cleanest compared to other generator options on the market.


When it comes to backup generators and fuel types, safety is essential regardless of flammability ratings. Each fuel type should be carefully considered and treated safely. For example, diesel fuel has a lower combustibility rating when compared to natural gas or propane but should still be treated with care to avoid any potential risks, hazards or accidents from occurring.


How readily available is the fuel type? What is the ease of access to obtaining more? Can you replenish the fuel supply if you expect to run your generator for prolonged periods? It’s important to consider these factors if faced with a power outage due to a natural disaster, severe weather such as winter storms and blizzards, or inclement weather such as torrential rain, downpours and high-speed winds.


Diesel generators are one of the most used backup generators in commercial or industrial applications because they are versatile and can meet backup power demands across various industries. These generators often have an onboard diesel base tank attached to the unit’s trailer, allowing the diesel fuel supply to be replenished easily as needed. While other types of portable generators are available, diesel is typically the best fuel for portable generators in commercial and industrial applications.

Find the Right Generator for Your Needs at Woodstock Power Company

If you’re struggling to determine the right generator type and what fuel you should run, talking to a professional can help narrow your choices. To discuss fuel types and get help deciding which generator fuel type best fits your needs, reach out to Woodstock Power Company’s customer service staff. Call us at 610-776-9104 or contact us online to get started today.

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