Today’s school bus fleets have four energy options: diesel, gas, electric, and propane (also referred to as LPG — liquefied petroleum gas — or propane autogas).

While diesel-powered school buses have long been the industry standard, comprising roughly 90% of the nearly 500,000 buses in operation today, environmental concerns are teeing up a shift to alternative fuel options.

“Increased standards on emissions in transportation have made it extremely difficult for diesel to comply and interest in alternatives to diesel has been on nearly every school district’s agenda,” explained Steve Whaley, alternative fuels manager for bus manufacturer Blue Bird Corporation.

Electric school buses are the most effective way to slash emissions, but higher acquisition costs — which are about three times the cost of a diesel bus — and infrastructure requirements are often prohibitive for school districts.

So, what do you do if you want to pivot away from diesel but electrification isn’t an option for your entire fleet? 

Whaley offers three reasons to consider propane.

Why Propane?

Propane-powered school buses allow school bus fleets to reduce emissions while also lowering operating costs. The following benefits of propane explain why.

1. Emissions

School buses that run on propane help school bus fleets dramatically reduce emissions compared to their diesel counterparts.

When comparing diesel and propane buses, the Propane Education & Research Council (PERC) found propane-powered buses:

• Emit virtually zero particulate matter (also known as particle pollution)

• Reduce nitrogen oxide (NOx) emissions by 96%

• Have engines that run 90% cleaner than mandated EPA standards

A West Virginia University study that compared a 2015 LPG-powered Blue Bird school bus with a 2014 ultra-low sulfur diesel Blue Bird school bus also found the same results.

“Using propane reduces harmful emissions, like NOx, by more than 90% compared to diesel, making it very easy to reach sustainability goals,” Whaley said.

With propane, emission reductions add up quickly. In 2018, 20 Pennsylvania school districts deployed approximately 1,000 propane school buses. The shift from diesel to propane has eliminated 5,000 tons of carbon dioxide per year across the districts.

2. Easy Transition

Unlike electrification, which typically requires a significant infrastructure investment, specialized technician training, and pristine maintenance conditions, using propane is very similar to using gasoline.

“The adoption of propane buses is much simpler than most imagine,” Whaley said. “It is exactly the same engine as the gasoline-powered bus but with a different fuel tank and injectors. There are several fuel tank capacity options, with the largest providing over 400 miles of range regardless of climate. It’s also an easy step for mechanics to transition to servicing a propane fueling system.”

Although propane isn’t as widely accessible as gasoline, school bus fleets don’t necessarily have to purchase LPG fueling equipment (tank, dispenser, and fuel management system) on site. Oftentimes, the fuel supplier will provide the necessary fueling infrastructure. Beyond installing scalable fueling infrastructure on site, other options include mobile fueling or temporary/portable systems.

“The most significant aspect of the propane alternative is the ease of obtaining fueling infrastructure,” Whaley said. “Propane suppliers acquainted with transportation fueling will provide the equipment needed to fuel any fleet size at no capital expense. A one- to three-year agreement with a locked-in fuel cost will secure this equipment, which dispenses 10 gallons per minute and can be easily scaled up or moved to another location.”

3. Total Cost of Ownership

Whaley said propane buses can cost up to 10% more than a diesel bus, but when looking at the total cost of ownership, school districts will still spend less to operate propane buses versus diesel.

Part of the reason is that propane costs less than diesel, and propane buses don’t require diesel exhaust treatments, like DEF and particulate matter filters.

“The less than 10% acquisition cost over a diesel bus is quickly offset by lower fuel costs, which are about 50% less than diesel,” Whaley said. “On average, school bus fleets operating propane buses have reported a $3,500 per bus per year savings over their diesel buses.”

Per Blue Bird’s findings, propane also wins on cost per mile. Without factoring in grants or incentives, here’s how the four fuel options compare:

1. Propane @ $1.20/gallon — $1.01

2. Diesel @ $3.50/gallon — $1.21 per mile

3. Gas @ $3.25/gallon — $1.26 per mile

4. Electric @.12/kWh — $2.25 per mile

For the 20 school districts in Pennsylvania, the total cost of ownership for their propane buses turned out to be around $143,000 less than diesel school buses.

What About Gasoline?

Gasoline is an option that comes with its own benefits, but gas-powered buses have a higher cost per mile and don’t yield the environmental advantages that come with operating propane school buses.

“Gas is the easiest step away from diesel. Everyone is familiar with gasoline and its ubiquitous infrastructure for fueling and even wider base of service technicians than diesel. It can provide the same range and operational duty cycle demands as diesel,” Whaley said. “It doesn’t address the need to aggressively pursue much lower emissions, but it is a step in the right direction to reduce maintenance costs compared to diesel.”

How to Choose the Right Option for Your School Bus Fleet

Although Whaley sees the advantages of propane over gasoline, diesel, and electric power, he said school districts need to weigh their options based on their individual circumstances.

“We can make the exact same bus with all four energy options. All of the alternatives to diesel can be a good fit if applied to the most appropriate operational duty cycle,” he said. “Considering the factors involved in selecting the right mix of alternative energy options for your fleet is key.”

When choosing an alternative fuel, factors to consider include:

• Capital expenditure

• Available energy to dispense into vehicles

• Fuel/energy costs and availability

• Range needed

• The local climate

Whaley recommends working with bus manufacturers, who can be a tremendous help in finding and transitioning to the right fueling option for your school bus fleet.

“Your bus dealer representatives have a tremendous amount of informational resources and experiences with other fleets near you that have adopted alternative-fueled buses,” he said. “They can help you identify funding opportunities in your area, energy and infrastructure providers with successful track records, and put you in contact with peers that you can benefit from their experiences.”