SUMMERVILLE, S.C. — South Carolina has acquired 26 propane school buses as part of its efforts to update its fleet.

The first of the new propane buses were unveiled in a ceremony in Summerville on Thursday.

South Carolina bought the Blue Bird Vision Propane buses to replace older diesel models. As previously reported, the state is working to update its fleet and to raise driver and technician salaries.

South Carolina is the only state that owns its entire school bus fleet, which is reportedly also one of the oldest in the nation. According to the South Carolina Department of Education (DOE), half of the state’s 5,582 buses are more than 15 years old.

"With aging diesel buses in our fleet, it was time to replace them, and propane was the option we thought worked best financially and environmentally speaking over the long term,” said Mike Bullman, director of maintenance for the state DOE.

The new propane buses were slated to go into service in Dorchester and Berkeley counties on Friday.

"These buses are not only twice as efficient as those 20-plus year old buses that they are going to replace but are also much cleaner burning," said Molly Spearman, state superintendent of education. "We are looking forward to the cost savings and exploring future uses for these buses around the state.”

Officials said that this is South Carolina’s biggest order of alternative-fuel school buses in the past 30 years. The state bought the buses from Blanchard Bus Centers, which recently became Blue Bird’s new dealer for South Carolina.

“We believe the state of South Carolina will begin to see immediate benefits from these new ‘clean’ buses,” said Joe Blanchard, president of Blanchard Bus Centers. “The financial savings should be noticeable from the beginning. An average propane bus saves a school district up to $3,500 per year in fuel costs alone.”

The Vision Propane bus is powered by Ford’s 6.8L V10 engine and Roush CleanTech’s propane fuel system. Sales of the Vision Propane increased 33% in 2016 compared to 2015, according to Mark Terry, Blue Bird’s chief commercial officer.

“These buses clearly work to save districts money, and are incredibly environmentally friendly,” Terry said.

Todd Mouw, vice president of sales and marketing at Roush CleanTech, added that propane “produces far less particulate matter and NOx emissions than diesel, so the buses don’t require expensive and difficult-to-maintain aftertreatment components to make them run clean.”