Propane is not cheaper than gasoline on a straight per-gallon basis, and it becomes even more expensive when you account for the energy difference between the two fuels. As of late 2025, the national average price for propane is $3.42 per gallon compared to $3.14 per gallon for regular gasoline, according to the U.S. Department of Energy. But the price gap widens further because propane contains less energy per gallon than gasoline, meaning you need more of it to drive the same distance.
Why Price Per Gallon Is Misleading
Comparing propane and gasoline by the sticker price at the pump misses a critical detail: a gallon of propane contains only about 73% of the energy found in a gallon of gasoline. The Department of Energy measures this using a unit called a gasoline gallon equivalent (GGE), which standardizes different fuels by how much energy they actually deliver. One gallon of propane equals 0.74 GGE, so you need roughly 1.35 gallons of propane to match the energy in a single gallon of gasoline.
That changes the math significantly. If propane costs $3.42 per gallon but you need 1.35 gallons to equal one gallon of gasoline, your effective cost is about $4.62 per gasoline gallon equivalent. Compare that to $3.14 for a gallon of regular gasoline, and propane costs roughly 47% more to travel the same distance. Even if propane prices dip below gasoline prices in certain regions or seasons, the energy penalty means propane almost always costs more mile for mile.
What It Costs to Convert a Vehicle
You can’t simply fill a standard car or truck with propane. The vehicle needs a dedicated fuel system, including a separate tank, fuel lines, and modified engine components. Professional conversion for a light- to medium-duty vehicle (Class 1 through Class 4, which covers most passenger vehicles, pickups, and delivery vans) runs between $7,000 and $9,000 including labor, according to the Propane Education & Research Council.
That upfront cost is a major hurdle for individual drivers. Fleet operators sometimes absorb it because they can negotiate lower propane prices in bulk and standardize maintenance across dozens of vehicles. For a single car owner driving 12,000 to 15,000 miles a year, the conversion cost alone would take years to recoup, and that’s only possible if propane were actually cheaper per mile, which it currently isn’t.
The Federal Tax Credit Has Expired
Until recently, a federal excise tax credit of $0.50 per gallon helped offset propane’s higher effective cost. That credit applied to propane sold or used as a motor vehicle fuel. However, the incentive expired on January 1, 2025, and Congress has not renewed it. Without that half-dollar discount per gallon, the economics tilt even further in gasoline’s favor for drivers making a purely cost-based decision.
Some states still offer their own incentives for alternative fuel vehicles, such as reduced registration fees, HOV lane access, or grants for fleet conversions. Whether any of those apply to you depends on where you live and how you use the vehicle.
Maintenance Differences Are Minimal
One argument for propane is that it burns cleaner than gasoline, which could theoretically extend engine life and reduce maintenance costs. Propane produces fewer carbon deposits and lower levels of certain exhaust pollutants. In practice, though, manufacturers of propane fuel systems recommend following the same oil change intervals and fluid specifications as the original gasoline engine. You won’t save meaningfully on routine maintenance by switching fuels.
Where propane does offer a slight edge is in fuel system cleanliness. Because it enters the engine as a vapor rather than a liquid, there’s less fuel washing (where liquid gasoline strips oil from cylinder walls) and fewer carbon buildups over time. This can contribute to a longer-lasting engine in high-mileage applications, but the benefit is difficult to quantify in dollar terms for a typical driver.
When Propane Might Still Make Sense
Cost isn’t the only reason people consider propane. It produces lower carbon monoxide and fewer particulate emissions than gasoline, which matters for indoor or enclosed operations like forklifts in warehouses. Fleet operators in industries where emissions standards or air quality regulations are tightening sometimes choose propane for compliance reasons, not fuel savings.
Propane also has a domestic supply advantage. The United States is a net exporter of propane, and prices tend to be less volatile than gasoline over long stretches. For large fleets that lock in fuel contracts, price stability can be worth more than a few cents per gallon. But for an individual driver asking whether switching from gasoline to propane will save money at the pump, the answer right now is no. Gasoline costs less per gallon, delivers more energy per gallon, and requires no expensive conversion to use.