Battery-powered electric buses are now whirring up and down Central Avenue in Albuquerque, N.M., ushering in what may be the next wave in low-emission transit vehicles.   "Central Avenue makes the perfect corridor for such an experiment," said Dayna G. Crawford, deputy director for ABQ RIDE, the city's transit agency. "With 15 percent of the city’s houses and 20 percent of the city’s jobs within a half-mile of the corridor, keeping the air clean should be a fundamental goal."   Albuquerque joins other cities like Stockton, Calif., in the march toward battery-powered buses. The San Joaquin Regional Transit District, which operates in Stockton, has a dozen electric buses on its bus-rapid-transit route. The district plans to purchase five more next year.   Battery-powered electric buses still represent just a tiny fraction of the thousands of buses in operation on any given day in America’s cities. In 2015, they amounted to 147 of new bus sales, according to the Center for Transportation and the Environment, an organization advocating for sustainable transportation. In 2017 the number of electric bus sales or commitments to place orders climbed to 556.    Meanwhile, prices for lithium-ion batteries continue to drop, helping to make the electric buses more affordable. A report by Bloomberg New Energy Finance cited a smaller than expected demand for electric cars resulted in an oversupply of batteries, making the power storage devices 23 percent cheaper in 2017 over 2016. The July 2017 report also noted “demand for batteries from electric buses far outstripped that of other passenger vehicles in 2016.”   "That's driving a lot of this," said Alan Westenskow, director of business development at Proterra, a California-based maker of battery-electric buses.     “It’s a solution that completely takes the place of a fossil fuel bus, in every single way,” Westenskow said.   Electric buses are also credited with being cheaper to operate and maintain due to fewer mechanical parts.   "Over the next period of 10 or 15 years, we believe that we’ll see a complete replacement of the fossil fuel bus industry, because you have the superior technology from a performance and economic standpoint,” said Westenskow.   Electric buses are not without their infrastructure needs. In Stockton the initial high-speed chargers cost RTD $349,000 and $600,000 for the second charger, said Terry Williams, a spokesman for RTD, adding the transit district will install a third charger next year at a cost of $600,000. The battery-powered electric buses, produced by Proterra, cost about $850,000 a piece.   As a comparison, a similarly sized bus powered by a diesel-electric hybrid engine are approximately $750,000, said Williams. Still, the price for electric buses continies to drop. In 2010, a Proterra bus cost about $1.2 million.    Albuquerque's 18-bus purchase cost $21.6 million. Officials estimate that cost will be repaid by $28.3 million in savings in maintenance and fuel costs over the next 12-year lifecyle of the electric buses.    The Institute for Transportation and Development Policy recently awarded Albuquerque’s $130 million new bus rapid trasit line with its Gold Standard, taking note of the number of doors on the bus which can open on both sides, ticketing and fare-collection that can happen prior to boarding, station infrastructure and other features, which combined with the dedicated bus travel lanes have led to not only quicker trips up and down Central Avenue, but more on-time arrivals. However, it was the simple fact that the new buses do not spew emissions that likely earned to transit agency the most points, said Bruce Rizzieri, director of ABQ RIDE.   But, it’s not just Albuquerque and Stockton adding electric buses to their fleets. San Jose, Calif., recently approved the purchase of 10 buses, while Greensboro, N.C., will add four buses and Shreveport, La., will add five buses, all of them made by Proterra. And the Utah Transit Authority in Salt Lake will place five battery-electric buses in operation in 2018. UTA currently operates 50 hybrid-electric buses and 47 CNG-powered buses, all within a fleet of 500, said Carl Arky, a spokesman for UTA.   "It’s not a political map. It’s not kind of a blue-state/red-state map. It’s everybody adopting this because it just makes sense," Westenkow said.    Officials in Greensboro say their primary motivation behind the switch to electric is cost.    "Even though the electric buses cost more up-front, we project a total lifetime — 10 years with 500,000 miles — savings of $340,000 per bus due to reduced maintenance and operating cost," said Adam Fischer, director of transportation in Greensboro, in an email. The city operates about 50 buses and plans to eventually replace its entire diesel fleet with electric vehicles.    “These electric buses can help us significantly reduce costs and greenhouse gas emissions, and represent a step toward our aspiration that an electric engine power every shuttle and bus on San Jose’s streets,” San José Mayor Sam Liccardo said in a statement.   The electric buses in San Jose, which cost about $750,000 each, will replace older CNG buses, can be operated at 19 cents per mile, far cheaper than diesel, which costs 84 cents per mile, according to Proterra officials.