For example, a full-size CNG transit bus costs $420,000 to purchase, while a similar diesel vehicle is about $370,000, said Randy Cloud, director of maintenance for the Metropolitan Tulsa Transit Authority. CNG prices are currently about one-third the cost of diesel, he said, though that price may climb as CNG becomes more prevalent.
"The payback and difference between CNG and diesel would be less than three years," Cloud said. He added that each vehicle has an expected lifetime of 12 years. Cloud said exact figures weren't available since CNG prices are expected to rise in the next decade, but if a $50,000 deficit can be made up in just three years, each bus could save more than $100,000 in its lifetime.
Mayor Dewey Bartlett said CNG saved the transit system nearly $400,000 on fuel in 2013. City trash trucks stick to the same system as their bus counterparts, he said. When one truck is retired, a new CNG truck takes its place.
Bartlett said evidence showing the long-term savings of switching to CNG vehicles made convincing skeptical people much easier. A number of city buses and trash trucks are already seeing significant savings, making future fleet conversion an even easier process, he said.
"People can come up with all kinds of reasons why they can't do things," Bartlett said. "When it comes down to it, it's usually fear or lack of knowledge. When you point out how cheap CNG is on a per gallon basis, many of those fears melt away."
Bartlett said city trash trucks that run on CNG have savings that trickle down all the way to Tulsans' pocketbooks.
"The city of Tulsa made a requirement at my request that anyone who bid on the (trash) service must use CNG-powered vehicles," he said. "That, in and of itself, is able to keep rates down and postpone rate increases. Rates will stay constant for a much longer period of time."
John Estus, a spokesman for the state Office of Management and Enterprise Services, said buying a CNG Department of Transportation pickup costs about $6,000 more than its traditionally fueled counterpart. But savings on fuel costs and maintenance — CNG burns cleaner than gasoline — can pay off that difference in a hurry.
All CNG stations near Tulsa reported prices under $2 per gallon, and some were nearly $2 per gallon less than traditional gasoline.
"I'm in the oil and gas business. I understand how the various markets work," Bartlett said. "It can be unknown, somewhat, how to anticipate what a market will do as far as fuel, because those markets are dictated by events in other countries. The CNG market forces are totally dependent on domestic events, which are much more predictable. The advantage of using our own domestically produced fuel is a very real advantage."
Cloud said more than half of Tulsa's city bus fleet are CNG vehicles. He said 27 of the city's 63 "fixed route," or larger buses, are now CNG, as are all but five of the 42 minibuses.
"The difference in (up front) cost between a CNG (fixed route) bus and a diesel bus is about $50,000," Cloud said. "It is more money up front, but the payback on it at this point in time is really fast."
Estus said the state purchased 242 Dodge Ram 2500 pickups last March thanks to an initiative led by Gov. Mary Fallin and Colorado Gov. John Hickenlooper. That initiative was aimed at getting major car makers to focus on creating lower-cost CNG "fleet" vehicles. Estus said the state also purchased a number of Honda Civics and some Chevrolet pickups.
As for the Dodge Rams, Estus said those are primarily used by Department of Transportation crews. Armed with a formula used to determine savings based on fuel costs and maintenance, Estus said each pickup will save the state about $9,000 per vehicle over a five-year period.
"As long as the cost of natural gas stays lower, it will be cheaper," Estus said. "I don't think anyone sees traditional fuel costs going down."
State Rep. Josh Cockroft said ODOT has saved more than $30,000 each month since purchasing those vehicles.
Earlier this month, a measure proposed by Cockroft to help counties convert their vehicle fleets to CNG and increase the number of CNG fuel stations across the state was approved by the House.
"What I like is that each county association and each individual county would be able to track each individual dollar saved and say. 'This is how much money we're saving,' " Cockroft said. "There will be some up-front costs involved, but at the same time, this is a long-term program that will save money."