The whole city, and the operator behind the numbers
Shenzhen finished turning every bus in the city electric by the end of 2017, 16,359 buses in total, run by 3 separate operators. It was the first big city bus fleet anywhere to reach 100%. Most of what is known about the cost and the charging problems comes from a World Bank study of just 1 of those 3 operators, Shenzhen Bus Group, known as SZBG, which ran close to 6,053 of the 16,359 buses, close to a third of the routes in the city.
What the subsidy changed
The World Bank built an 8 year cost model with SZBG for its main bus, the BYD K8, covering the purchase price, energy, maintenance, tax and resale value. Bought with no government help, an electric K8 cost 2.02 million yuan to own over 8 years, 21% more than a 1.67 million yuan diesel bus. China paid a national purchase subsidy of 500,000 yuan for each bus over 10 meters long, bought during or before 2016, and Shenzhen added a local subsidy on top. With both subsidies counted in, the same electric bus cost 1.07 million yuan over 8 years, 36% less than the diesel bus. The swing from paying 21% more to paying 36% less came from policy, not from the battery getting cheaper on its own.
Values are rounded to the nearest thousand yuan from the World Bank cost model for the BYD K8, which covers the purchase price, energy, maintenance, tax and resale value across 8 years.
Show the numbers
| Diesel bus | 1670 |
| Electric with subsidy | 1065 |
| Electric without subsidy | 2021 |
Where the buses charge
Finding room to charge close to 6,000 buses was the harder problem. SZBG had to find land for charging depots in a city that had set none aside, then negotiate transformer and grid capacity increases zone by zone. By June 2019 the operator had 1,707 charging terminals at 104 stations, run by 9 different charging companies, about 1 terminal for every 5 buses, short of the 1 for every 4 it had targeted. Starting in 2016, SZBG let 4 buses share 1 terminal overnight at a slower charging speed, which saved the labor cost of moving buses around a full depot at night.
The battery question nobody measured
No source measured how much charge a Shenzhen bus battery loses over time. What is on the record instead is the warranty the bus suppliers offer, 8 years on the battery, the motor and the controller together, covering the whole working life SZBG expects from a heavy duty bus. A traditional diesel bus maker typically covers its vehicle for 2 to 4 years. Taking on 8 years of financial exposure on the battery is the clearest sign available of how confident the supplier is that it will last.
The diesel figure is a typical range for a traditional diesel bus maker. The electric figure is the warranty offered by the bus suppliers to SZBG, covering the battery, the motor and the controller together.
Show the numbers
| Electric bus | 8 years |
| Diesel bus | 2 to 4 years |
The wider count
Shenzhen Bus Group buses saved 194,000 tons of carbon dioxide in 2018, calculated from an emissions factor of 51,876 grams saved per 100 kilometers, multiplied by the 374.11 million kilometers the fleet covered that year. The World Bank recommended the SZBG case study to 189 member countries. Nearly 700,000 electric buses now run worldwide, more than 90% of them in China. A separate 2025 report from the World Resources Institute independently found the same 36% lifetime cost advantage that the World Bank calculated for SZBG, without repeating the calculation itself.