Last year, Bengbu Bus made its first purchases, when it bought 30 electric buses from BYD, while this year it made its biggest investment in electric vehicles by purchasing 500 electric buses and 62 hybrids from BYD. It is also leasing 138 electric buses from the same manufacturer.

Lyu, the official, said the investment was partly a result of the local government's strongest-ever emphasis on improving air quality and its efforts to win the National Civilized City title, which is awarded by the Central Commission for Guiding Cultural and Ethical Progress.

The commission, established in 1997, is one of the Communist Party of China's most important ideological steering bodies.

The level of public service and residents' comments about urban management are highly influential when the commission is evaluating contenders for the title, which was awarded to Bengbu last month. Lyu believes the introduction of clean energy vehicles by Bengbu Bus contributed to the city gaining the award.

While Bengbu has only recently begun using clean energy vehicles, Qingdao, a well-known tourist spot in Shandong province, has six years' experience of the practice. The coastal city, which has a population of 9.2 million and was visited by about 80 million tourists last year, operates nearly 10,000 buses.

Although the city stopped buying traditional buses in 2011, many will remain in use until they are no longer serviceable. "The traditional buses will not be replaced until they are old enough to be abandoned," said Yuan Haibo, head of the Qingdao traffic and transportation bureau.

This year, Qingdao has spent 1.1 billion yuan on 914 electric buses, the bureau said.

Recharging facilities

According to Sa, 355 charging poles for electric buses have been erected at 28 stations across Bengbu. Each pole can charge two buses simultaneously, so there are enough to meet the needs of Bengbu Bus. Recharging operations are usually conducted after 10 pm, when the price of electricity is at its lowest.

There are not as many charging poles in Qingdao, though, because the scale of operations in the larger city would make the practice too expensive.

"Building enough charging poles here would be far more difficult," Yuan said.

In the past six years, Qingdao has used a range of methods to meet the demand for recharging services. In 2011, State Grid Co built the Xuejiadao bus terminal, the country's first supply station for charging electric bus batteries, in the city.

"The terminal, in Qingdao's West Coast New Area, received investment of 200 million yuan, and was designed to meet the needs of 200 electric buses," said Wang Xianjun, deputy general manager of the Zhenqing Bus Co, which operates in the area.

"The terminal's biggest advantage is that it is a superfast recharging facility."

Since 2011, six similar stations have been built in the city, but they gradually became smaller in scale as a result of the high construction and operating costs.

"For every two buses, each station must keep an extra set of batteries in reserve, which means we have to spend more money and build more storage facilities," Wang said, adding that each set of batteries can weigh 2 metric tons, which makes them hard to replace.

In 2014, State Grid adjusted its program and laid greater emphasis on the development of fast-charging poles－which allow buses to obtain a supplementary power boost－while providing enough slow-charging poles to meet demand.

"Ten minutes of fast-charging allows a bus with a low battery to run for an extra 30 kilometers," Wang said.

However, he conceded that the method only works for medium-sized buses, whose batteries lack the capacity to allow them to operate all day on one charge. He expressed the hope that technological breakthroughs will improve capacity and provide smaller batteries so buses will be able to carry more passengers.