Propane vs. Diesel Generator: Pros and Cons

Mobile generators are critical on construction sites for powering tools and machinery and at event sites for running lights, heat, air conditioning and sound equipment. Many business owners and homeowners also depend on generators during power outages. Diesel generators have been the standard for years, but as the impacts of climate change accelerate, so does the interest in cleaner temporary power. If you’re weighing a propane generator as compared to a diesel generator, understanding the differences will help you make an informed decision.

Propane vs diesel generators: The key differences

All mobile generators provide power where and when you need it. But emissions, fuel costs, maintenance costs and other considerations factor into whether a propane generator or diesel generator will best fit your needs.

Note that some propane generators, such as the JuiceBox from Evergeen Mobile Power, can run on either propane (LPG) or, if a gas hookup is available, natural gas. Some duel-fuel propane generators can also run on gasoline.

Carbon emissions and other air pollutants

Despite Tier 4 regulations designed to reduce nitrogen oxides and particulate matter from diesel engines, diesel emissions contain significantly higher levels of nitrogen oxides and particulate matter than propane emissions. In addition, diesel produces 17% more carbon dioxide than propane. If you’re concerned about air quality and emissions, propane is the clear choice.

Fuel costs

Diesel has a higher energy density than propane, producing 128,700 BTUs per gallon compared to 84,942 BTUs for propane. In other words, assuming identical engine efficiency, you’ll get more energy from a gallon of diesel. How much of a cost difference that makes depends on the fuel price. Diesel typically costs more than propane, but if the price difference in your area is less than 33%, you’ll still spend less on fuel by using diesel.

Fuel availability and shelf life

Most gas stations sell diesel fuel, and many home improvement and convenience stores carry propane. Fuel delivery services offer both. No matter which you choose, it’s vital to follow regulations for on-site storage.

Diesel fuel degrades over time, lasting about one year in storage with no special treatment. Propane lasts for decades, with no expiration date.

Smell

Diesel generators produce dark smoke and a characteristic unpleasant odor. Propane exhaust is virtually odorless and colorless.

Convenience

Propane generators are more convenient than diesel generators in several ways. First, they don’t require diesel exhaust fluid to burn cleanly, as diesel generators do.

Second, propane generators start easily in most conditions. In cold weather, diesel can turn to jelly, making diesel generators difficult to start.

Third, propane generators aren’t susceptible to “wet stacking.” When diesel generators run with low loads over a prolonged period, they may fail to completely burn the fuel, which becomes tainted with carbon. This “wet stacking” causes sputtering, rough running and smoking.

One potential downside of propane generators: Some require a separate fuel tank, which takes up space and requires installing a connection. Others, such as the JuiceBox, have an onboard propane tank.

Maintenance costs

Both diesel and propane generators need oil and fuel service every 500 hours, but service costs less for propane generators. Diesel generators also require fuel tank polishing, fan belt replacement and coolant adjustment every 2,000 hours. Maintenance costs can ultimately run about 40% less with a propane generator.

Rental costs

You’ll typically pay less to buy or rent a diesel generator than a propane generator. If your budget is tight, consider the total costs of fuel, maintenance and equipment rental before you make a decision.

The bottom line: Diesel generators are still the most economical choice in many cases. But propane generators are eco-friendlier. They offer reliable startup and lower maintenance costs, and they don’t foul the air with unsightly smoke or a rotten egg smell.

To reduce generator emissions even further and slash fuel consumption, pair a propane generator—or better still, a zero-emissions hydrogen generator—with a battery energy storage system for a hybrid power solution.

Propane generator safety tips

If you choose a propane generator, it’s important to follow recommended operating precautions including:

• Not using the generator in sealed or partially enclosed indoor areas, where carbon monoxide can build up.
• Locating the generator 20 feet from doors, windows and vents to ensure carbon monoxide isn’t sucked inside.
• Keeping the generator away from sources of fuel vapors, such as appliances, that could ignite the generator’s pilot light.
• Placing the generator in a covered area where water from rain, snow or other sources won’t puddle under or around it.
• Not using the generator in wet or rainy conditions or touching it with wet hands due to the risk of electrocution or explosion.
• Always plugging in equipment or appliances using a heavy-duty outdoor-rated cord with the correct wattage. The cord should be free of cuts and tears.
• Turning off the generator and allowing it to cool before you refuel it. Propane spilled on a hot engine can ignite.
• Getting a professional to install large, on-site propane storage tanks and fuel lines to avoid leaks.

Visit our online marketplace to browse our selection of generators or stop by your nearest United Rentals branch and speak with a representative.