Nio founder William Li predicted a higher penetration rate of 90%.

The central government would like 20% of new cars sold to be new energy vehicles by 2025.

New energy vehicles refer to battery-powered and hybrid cars. The category accounted for more than 10% of new car sales in China in March, and grew to 11.4% in May, said Wang Chuanfu, founder of BYD

He forecast that the penetration rate would surge to more than 70% in 2030. That's according to a transcript the company provided of his remarks at the China Auto Chongqing Summit held June 12 and 13.

William Li, founder and CEO of electric car start-up Nio, was more optimistic. He predicted that so-called smart electric cars would account for 90% of new car sales in 2030, according to Chinese media reports.

Nio did not have anything to add when contacted by CNBC. The U.S.-listed automaker leads its start-up peers in terms of monthly deliveries.

But Nio's deliveries of 6,711 cars in May fell from 7,102 in April, remaining well below that of BYD.

In May, BYD said its new energy passenger car sales rose 23% from the prior month to 31,681 vehicles, of which just over half — or 18,711 — were powered only by batteries.

The company's Han sedan ranks among the five best-selling new energy vehicles sold in China — just behind Tesla's Model 3 and Model Y for the first five months of the year, according to the China Passenger Car Association.

In first place is a budget electric car, the Wuling Hongguang Mini, developed under a General Motors' joint venture in China.

Chinese brands to dominate

Many foreign automakers such as Volkswagen have looked to launch electric cars in China first, where sales of battery-powered vehicles have gotten a boost from central government subsidies and other preferential policies.

Beijing would like 20% of new cars sold to be new energy vehicles by 2025.

As the local new energy vehicle market grows, BYD’s Wang said he expects Chinese car brands will be able to account for 60% by 2030, thanks partly to their grasp of core technology.