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For substantial standby or prime-power requirements, the fuel choice generally narrows to diesel or natural gas. Both are established, dependable options, and each comes with tradeoffs shaped by your site, budget, and tolerance for risk.
We sell and service diesel and natural gas generators every day, from 20 kW standby units to prime-power systems above 2,000 kW. We’re not committed to one fuel over the other. Our team installs, maintains, and troubleshoots both across hospitals, data centers, manufacturing facilities, and commercial properties nationwide.
We spoke with members of our sales and service teams to compare the options as we would in a conversation with a customer: with practical figures, honest tradeoffs, and no glossing over the details. The full discussion is in the video above. This guide covers the same ground in writing.
In brief, the decision hinges on two things: how frequently the generator will operate and how much fuel-supply risk you can accept. Cost, emissions, maintenance, and permitting all follow from those considerations.
What Fuel Options Are Available?
Commercial and industrial generators can use four main fuel types, although diesel and natural gas account for most large-scale discussions.
Diesel is a liquid fuel kept in tanks at the site. Its high energy density delivers substantial power from a relatively small volume of fuel, while on-site storage allows the generator to operate independently. The fuel is available beside the unit, without a supply line.
Natural gas comes through a pipeline, providing a continuous fuel source under normal conditions. It burns cleaner than diesel, requires no on-site fuel tank, and avoids fuel deliveries and tank upkeep. Where a gas connection is already available, the supply is generally at hand.
Gasoline and propane are also used, but far less often for commercial-scale power. Gasoline is typical for small portable generators, though it has a shorter storage life and is less suitable for demanding applications. Propane can suit remote locations and smaller installations. It burns cleanly, like natural gas, but storage requirements and cost at industrial scale often lead buyers to consider diesel or pipeline gas instead.
The fundamental distinction between diesel and natural gas is how fuel reaches the generator: it is stored on-site or delivered through a pipeline. That difference—tank versus pipeline—shapes nearly every comparison that follows, including reliability, cost, emissions, maintenance, and industry preferences.
Which Fuel Will Be Available When I Need It?
Reliability is often the leading consideration in this choice. The difference between stored fuel and pipeline supply is especially important here.
The Diesel Advantage: Fuel Independence
A diesel generator draws from a tank located on-site. It doesn’t need an outside supply line or depend on a utility for fuel. During a grid failure, natural disaster, or other emergency, it can keep running while fuel remains in the tank. Depending on tank capacity and load, that may mean 12 to 96 hours of operation, with refueling possible as needed.
As Tyson Peyton from our sales team explains:
“Virtually no matter what the emergency is, it’s not going to interrupt your fuel supply. It’s not going to interrupt your ability to back up your building.” — Tyson Peyton, Sales
This independence is why diesel is widely selected for life-safety applications. When we asked our service team what they encounter in the field, the response was direct:
“Most hospitals, all that. It’s all diesel.” — Allen, Service Technician
That doesn’t mean a natural gas generator cannot serve a hospital. Rather, its risk profile may not be the right fit. When uninterrupted electricity is critical to patient safety, facilities often favor a fuel source that does not depend on infrastructure beyond their property.
The Natural Gas Advantage: A Steady, Convenient Supply
For facilities that operate generators regularly or for extended periods, natural gas has a significant benefit: there’s no on-site tank to run dry. Pipeline delivery removes the need to arrange fuel deliveries, monitor tank levels, or manage stored fuel that may deteriorate or become contaminated. The gas supply is available through the line.
This can make natural gas a good match for manufacturing plants with around-the-clock production, data centers requiring extended power, and facilities that use generators for peak shaving to lower utility demand charges. When a generator runs for thousands of hours a year, avoiding fuel-handling tasks can simplify operations.
“Natural gas can be really nice because they don’t have to worry about fuel supply. So there’s advantages and pros and cons.” — Tyson Peyton, Sales
The Risk to Keep in Mind
One important tradeoff gets overlooked: natural gas arrives through pipelines, which are part of a larger network. If that network is disrupted, the fuel supply can be interrupted too.
Tyson explained the point with a clear example:
“Earthquake. It cracks the ground. Fuel lines are in the ground. Suddenly everybody downline of that break doesn’t have natural gas. And everybody on that side of that crack with a diesel tank sitting out, their generator’s working just fine.” — Tyson Peyton, Sales
The concern isn’t limited to major disasters. During a widespread outage, many natural gas customers connected to the same line may be drawing from the supply at once. Tyson describes it this way:
“It’s a vascular system. And if you have enough bleeds in a vascular system, there’s not enough pressure to power all the components.” — Tyson Peyton, Sales
This isn’t to say natural gas is unreliable. Where pipeline infrastructure is stable and conditions are normal, it can be highly dependable. But if your backup plan must account for extreme scenarios, dependence on that pipeline is a key factor to consider.
In short: Diesel offers greater independence, while natural gas offers convenience. The best fit depends on the type of disruption you need to prepare for.
How Much Fuel Will I Use?
Once you’ve answered the reliability question, efficiency is usually the next concern for buyers: how much fuel does each generator type use, and what does that mean in real-world operation?
In short, diesel contains more energy in a smaller volume. Its energy density is considerably higher than natural gas, so each unit of fuel delivers more power. For a practical comparison, here’s the approximate diesel consumption at 75% load for several common commercial generator sizes:
A 75–100kW generator uses about 5–6 gallons per hour. For a 150–200kW unit, expect around 8–11 gallons per hour. A 500kW generator uses roughly 24 gallons per hour, while a 1000kW unit consumes close to 47 gallons per hour.
Actual consumption depends on factors such as the engine manufacturer, maintenance, elevation, and ambient temperature, but these estimates provide a useful starting point for planning. Consult our complete fuel consumption charts for figures by generator size and load level.
Because natural gas has a lower energy density, a generator needs a greater volume of it to produce the same output. Consumption is measured in cubic feet per hour rather than gallons. That may seem like a drawback, but the better choice depends on how you’ll operate the generator.
For standby use, when the generator runs only occasionally and annual runtime amounts to hours or days, diesel’s concentrated fuel storage is a major advantage. A full base tank provides a predictable runtime without relying on an external fuel supply. Fill the tank, keep it maintained, and the generator is ready when needed.
For continuous or prime power, with operation lasting thousands of hours each year, the balance can change. Natural gas generally costs less per kilowatt-hour and tends to have more stable pricing than diesel. Over long runtimes, those savings can accumulate. Natural gas also avoids diesel fuel polishing and tank upkeep, as well as the possibility of stored diesel deteriorating over time.
Bottom line: Diesel offers compact fuel storage and strong efficiency under high loads. Natural gas may be the better fit for extended prime-power use, where lower fuel costs can add up across thousands of operating hours.
How Do Emissions Affect Permitting?
Natural gas offers a clear emissions advantage. Compared with diesel, it generally produces less nitrogen oxide (NOx), particulate matter, and carbon dioxide. For sites subject to strict air-quality rules or organizations with ESG goals, cleaner emissions may make the permitting process more straightforward.
“A lot of your government installations or facilities that are worried about EPA and air pollution guidelines, a lot of times they’ll explore natural gas and propane just because those are naturally cleaner burning. And it’s almost always easier to permit natural gas units because of the cleanliness of their emissions.” — Tyson Peyton, Sales
Diesel generators typically emit more NOx and particulates. To comply with current Tier 4 Final standards, newer diesel models use exhaust-treatment equipment such as selective catalytic reduction (SCR) and diesel particulate filters (DPF), as well as a diesel exhaust fluid (DEF) tank. These systems help control emissions, but they also bring additional components, upkeep, and expense.
The Tier 4 Caveat: Operating Load Is Critical
Older Tier 2 and Tier 3 diesel generators can usually operate at lower loads, sometimes around 40–50%, without major concerns. Tier 4 Final models require more careful load management.
Particulate filters rely on heat to work effectively, and the engine needs sufficient load to generate that heat.
“The Tier 4 Final is a whole different animal. If you’re not running a Tier 4 Final generator nice and hot, up around 85-90% of that load, then there’s a lot of particulates and issues getting through that exhaust system that those filters are catching. So those filters clog up very quickly.” — Tyson Peyton, Sales
A clogged DPF can trigger fault codes and prevent the generator from starting. Filter cleaning or replacement can be costly, and the resulting downtime may be unexpected. In some cases, the unit may shut down rather than simply reduce its output.
“You can’t even run it at less power. You’ll get codes. You’ll have to reset the codes. Clean up the filters.” — Tyson Peyton, Sales
When choosing a Tier 4 Final diesel generator, match its capacity closely to the load it will actually serve. An oversized unit operating under light load may lead to costly issues. Some models include load-compensation features to help maintain operating temperature at lower loads, but confirm that the specific unit has this capability.
There’s also a difference technicians may notice during service. Glen, one of our technicians, says engine oil in a natural gas generator can remain visibly cleaner for longer than oil in a comparable diesel unit.
Both types still follow the same 250-hour or annual service interval. Even so, the oil’s appearance offers a visible indication of how cleanly natural gas burns inside the engine.
In short: Natural gas can make emissions compliance simpler. Diesel can also meet applicable standards, but Tier 4 Final systems bring additional maintenance considerations, making proper sizing especially important.
What Should You Expect to Pay?
Cost is an essential part of the decision, and insight from someone who works with generator pricing every day can help put the differences in perspective.
Equipment Price: The Difference Grows at Higher Capacities
For smaller commercial generators, diesel and natural gas prices may be fairly close. Tyson explains how the gap changes as units get larger:
“When you have a small unit, 35kW, 40, 50 kilowatt, a lot of times those prices are pretty comparable between a diesel and a natural gas. But as you get larger, the gap between natural gas and diesel gets much, much bigger when it comes to purchasing the equipment.” — Tyson Peyton, Sales
The difference comes down to engine design and fuel energy density. Natural gas engines generally need to be larger to deliver the same power as diesel engines, which can mean more materials and higher equipment costs.
“Where a unit could be 6 or 700,000 in diesel, it might be in the millions, 1.2 million in a natural gas.” — Tyson Peyton, Sales
Those figures refer to units with comparable output. At higher capacities, the natural gas equipment purchase price alone can approach twice the cost of a diesel model.
Installation: Diesel Is More Straightforward
Equipment price is only part of the picture; installation can look quite different for each fuel. A diesel generator typically needs a concrete pad and a fuel fill point. In most cases, you position the unit, fill its tank, and it’s ready to operate.
“With a diesel, wherever you put the pad and the generator, you just fill it with fuel. That’s all you need. You don’t have to run fuel lines to it.” — Tyson Peyton, Sales
Natural gas involves additional steps. You’ll need a pipeline connection, a pressure regulator, and gas piping from the meter to the generator. The lines must be pressure-tested, and installation costs can add up depending on the run length and site conditions.
One detail that can surprise buyers: having a natural gas connection at your property doesn’t necessarily mean the supply is sufficient to power a generator.
“Just having natural gas doesn’t mean you have enough natural gas to run the equipment. Sometimes you actually have to upgrade your system so it can support the generator.” — Tyson Peyton, Sales
Pipe size, available pressure, and the site’s overall demand all matter. Tyson advises checking the engine’s fuel-consumption specifications and confirming capacity with your gas provider before making a decision. If other appliances or equipment already use natural gas, their consumption also affects how much supply remains available.
The Long-Term Cost Crossover
This is where the comparison gets more nuanced. Natural gas equipment can cost more to purchase and install, but natural gas is often less expensive and more stable in price than diesel. For generators with high annual run times, those fuel savings may eventually make up for the higher initial cost.
“There’s kind of a crossover point. A gas unit is often more expensive to buy and install, but costs over time can come down because of the difference in fuel prices.” — Tyson Peyton, Sales
For standby generators that operate only a few dozen hours each year, diesel is usually less expensive over the equipment’s lifetime. Its lower purchase price, simpler setup, and limited fuel use can make the extra cost of natural gas difficult to justify.
For prime or continuous-power needs that involve thousands of operating hours annually, the balance can change. Lower fuel costs per kilowatt-hour, fewer fuel-delivery arrangements, and no storage tank to maintain can make natural gas more appealing over time.
Bottom line: Diesel generally costs less to purchase and is simpler to install, while natural gas can cost less to operate. The better value depends on annual operating hours and local fuel prices.
What Does Routine Maintenance Involve?
Diesel and natural gas generators share the same basic service schedule: every 250 operating hours or once a year, whichever comes first. What technicians inspect and service differs by fuel type.
Diesel Maintenance
Diesel generators need closer attention to fuel management. Stored diesel can deteriorate, water may collect in the tank, algae can develop, and contaminants can build up if the fuel is neglected. Fuel polishing at least once a year helps keep stored fuel clean and usable. Fuel filters also need regular inspection and replacement according to schedule.
Tier 4 Final units have additional requirements: maintaining the DPF and SCR systems and keeping the DEF tank supplied. As noted in the emissions section, running out of DEF can cause automatic derating, while operating under insufficient load can clog particulate filters. These procedures are manageable, but they still need to be part of regular maintenance.
Natural Gas Maintenance
Natural gas removes fuel storage from the maintenance routine. There’s no tank to manage, stored fuel to polish, or delivery schedule to coordinate; gas comes directly from the pipeline. Service is focused more on the engine and fuel system, including spark plugs, ignition components, and gas-train parts such as pressure regulators and shut-off solenoids. Despite burning more cleanly, natural gas generators still follow the same 250-hour or annual service interval.
Safety Considerations
Both fuel types have established safety records when equipment is installed and maintained correctly. Diesel has a higher flash point than gasoline and is less volatile than many people expect. A spill can be messy and must be cleaned up properly, but it does not present the same immediate volatility concerns as some other fuels.
Natural gas installations call for proper ventilation and leak detection. The main concern is gas collecting in an enclosed area. Modern systems help manage this risk with automatic shut-off solenoids, gas detectors, and appropriate enclosure ventilation. Gas connections can be checked by applying a soapy solution to joints and unions; bubbles can indicate a leak.
A Practical Factor to Weigh
For urban sites or enclosed installations with limited access, natural gas’s simpler fuel-supply setup can make service visits easier. There’s no need to bring in a fuel truck, inspect a storage tank, or check as many fuel-delivery components.
At remote sites or in dusty, demanding environments, diesel’s established mechanical durability and broad base of service experience may be more practical. Many technicians have hands-on experience with diesel equipment, and parts are often more widely available.
Bottom line: The service intervals are alike, but the checklists differ. Diesel requires more fuel-system attention, while natural gas calls for more work on ignition and gas-train components. Neither is automatically more difficult to maintain; each has its own priorities.
Which One Is Right for Me?
The decision largely comes down to two things: how frequently the generator will operate and what the consequences would be if its fuel supply were disrupted.
Choose diesel if:
You mainly need standby or emergency power. Fuel independence is essential for life-safety or mission-critical operations. The generator will run only occasionally—perhaps a few hours or a few dozen hours each year. Your site is remote or lacks dependable pipeline service. Or you’re looking for a straightforward installation with a lower initial price.
Choose natural gas if:
Your generator will provide continuous or prime power for thousands of hours annually. You have reliable pipeline access and want to reduce fuel costs over time. Lower emissions could make permitting easier or help meet sustainability goals. You’d rather avoid on-site fuel storage, deliveries, and related upkeep. Or you plan to reduce utility demand charges through peak shaving.
When the choice isn’t clear-cut:
Some applications can make a case for either fuel. A data center may favor diesel for Tier III/IV fuel independence, or consider natural gas when pipeline service is dependable and sustainability is a priority. A manufacturing site with demanding, fluctuating loads may choose diesel, while a facility with steady, around-the-clock production may prefer natural gas. The right fit depends on your load profile, local fuel costs, and your tolerance for supply interruptions.
Hybrid systems offer another possibility. Bi-fuel generators can change from one fuel to another, while dual-fuel models combine fuels—often using diesel to start and natural gas during steady operation. They won’t suit every site, but they may be worth considering when you need both supply independence and efficient, long-duration operation.
The short answer:
If the generator must start during an emergency and operate without relying on fuel infrastructure beyond your property, diesel is usually the stronger fit. If it will run routinely under predictable loads and your natural gas supply is dependable, natural gas may cost less over the equipment’s lifetime.
Which Industries Use Each Fuel?
This industry-by-industry overview reflects common choices in real-world applications.
Hospitals and Healthcare generally rely on diesel for primary backup. Life-safety systems call for a fuel source independent of the pipeline. Where permitted, natural gas may support non-critical loads, while diesel typically serves as the main backup.
Data Centers choose according to their priorities. Diesel can provide the Tier III/IV independence many uptime plans require. Natural gas is gaining consideration at sites with dependable pipeline service and sustainability goals.
Manufacturing often uses natural gas for production lines that operate continuously. Diesel may be a better match for heavy or fluctuating loads, or for facilities without access to a gas pipeline.
Peak Shaving usually favors natural gas. To offset utility demand charges during peak periods, facilities need generators that can run for extended stretches, making natural gas’s lower fuel cost a key consideration.
Crypto Mining commonly turns to natural gas for a similar reason: keeping equipment running for long periods while managing fuel expenses.
Grocery and Cold Storage operations are increasingly considering natural gas, although diesel remains a common standby choice to help protect inventory during outages.
Agriculture and Remote Operations often depend on diesel. A quarry, irrigation system, or distant construction site may not have pipeline access. These applications need a generator that can remain on site, fueled and ready to operate.
Oil and Gas operations use both fuels. Natural gas can serve wellhead sites with fuel readily available and long operating hours. Diesel suits remote field locations where portability and independence are important.
Telecom typically uses diesel at mission-critical tower sites. Natural gas may be chosen for urban installations where quieter operation and lower emissions are preferred.
Property Management choices depend on the building, location, and intended use. Urban commercial properties with existing gas service may be well suited to natural gas. Sites focused on emergency backup and simpler fuel logistics may favor diesel.
Ready to Choose?
Still weighing which fuel is right for your facility? Our team works with and services both diesel and natural gas generators, from 20kW standby models to 2,000kW+ prime power systems. We can help assess the costs for your particular application.
FAQ: Diesel or Natural Gas Generators
Does a natural gas generator cost less than a diesel generator?
For smaller units (35–50 kW), prices are often similar. At higher capacities, diesel equipment usually has a lower purchase price, sometimes by a wide margin. A diesel unit priced at $600,000–$700,000 might cost $1.2 million in natural gas for the same output. Natural gas generally costs less as a fuel, though, so over time it may offer a lower total cost of ownership for applications with high runtime.
Why do hospitals choose diesel generators?
Fuel independence. Diesel generators keep fuel on site and don’t rely on an outside utility or pipeline. During an emergency, they can operate as long as fuel remains in the tank. For life-safety uses where continuous power is essential, that independence can be the deciding factor.
What is Tier 4 Final, and why is it important?
Tier 4 Final is the current EPA emissions standard for diesel generators. Compliant units use diesel particulate filters (DPF) and selective catalytic reduction (SCR) systems to reduce emissions. Buyers should note that these generators need to operate at 85–90% load to function properly. At light loads, a Tier 4 Final unit can clog its particulate filters, produce fault codes, and shut down.
Will a natural gas generator work during a power outage?
Yes, provided the gas pipeline remains operational. Natural gas service is separate from the electrical grid, but pipelines can be affected by natural disasters, ground damage, or exceptionally high demand during widespread outages. If your backup plan needs to cover these situations, diesel’s stored on-site fuel can offer greater certainty.
How much diesel does a generator consume per hour?
Consumption depends on generator size and load. At 75% load, a 100 kW diesel generator uses about 5–6 gallons per hour; a 500 kW unit uses around 24 gallons per hour, and a 1,000 kW unit nearly 47 gallons per hour. Refer to our full fuel consumption charts for details by generator size and load percentage.
Is maintenance different for diesel and natural gas generators?
Both typically follow a 250-hour or annual service schedule, but the maintenance tasks vary. Diesel service includes fuel-system care, such as fuel polishing, filter replacement, and tank checks. Tier 4 units also require attention to their DPF and DEF systems. Natural gas maintenance centers on spark plugs, ignition systems, and gas train components.
Neither type is necessarily more difficult to maintain; each simply needs a different kind of attention.
