The STM could save $3,500 per day with a full fleet of electric buses, study shows

A passenger boards an STM bus on Nov, 14, 2025. (Christopher Katsarov/The Canadian Press)

A fleet of fully electric buses would save the Société de transport de Montréal (STM) $3,500 per day, according to a study by Concordia University researchers.

The research team, led by Xuelin Tian — who completed her PhD at Concordia this year and is currently a postdoctoral fellow at Laval University in Quebec City — is the first to conduct this type of study in a winter environment.

“The motivation for this study came from the urgent need to decarbonize public transportation while ensuring reliable service in regions with demanding climatic conditions such as Montreal, unlike other studies conducted in temperate climates,” she explained in an interview with The Canadian Press.

“The cold adds challenges by increasing the demand for vehicle heating and reducing battery performance. Slippery streets also reduce the performance of regenerative braking, which contributes to battery recharging.”

Thanks to links established with the STM during previous research, her team was able to collect detailed data at 66,000 points spread across 56 routes covered by 40 fully electric buses, Flyer XE40 vehicles.

The amount of data collected is impressive.

“We analyzed the records of approximately 50,000 routes in total, which is unique, thanks to the collaboration of the STM. We have never had access to such an operational database before,” said Tian.

More energy in winter

It comes as no surprise that electric buses use more energy in winter, that consumption is optimal in summer, and that results in spring and fall fall somewhere in between.

In winter, a battery electric bus (BEB) consumes 1.7 kilowatt hours per kilometer, compared to 1.4 kilowatt hours per kilometer in summer, which is 26 per cent more in cold weather.

Regenerative braking also suffers in cold weather. Recovered braking energy averages 45.8 per cent, with a peak of 50 per cent in summer and a low of 32 per cent in February, which is usually the coldest month.

“Regenerative braking is more efficient in summer, but it is also related to speed. The best regenerative braking performance is achieved with vehicles traveling at 30 to 50 kilometers per hour. At this optimal speed, 50 per cent to 60 per cent of braking energy is recovered,” Tian explained.

She added that she was surprised by the fact that the incline of the routes — Montreal has no shortage of hills — has little influence on energy consumption.

On reflection, however, this is an immutable law of physics: what goes up must come down. So, while energy consumption increases on the way up, it falls below average on the way down and, better still, the descent has a positive influence on regenerative braking.

Much cheaper than diesel

Where the study’s findings become more interesting, however, is when they are compared to diesel buses. The operating costs of EBAs are on average 40 per cent to 60 per cent lower than those of diesel vehicles, summer and winter combined.

And what about hybrid buses? Their energy performance falls between that of EBAs and diesel vehicles.

“Typically,” the study says, “electric buses maintain the lowest operating costs, between $20 and $150 per day. In contrast, diesel buses have the highest daily operating costs, often exceeding $300, particularly in winter due to higher fuel consumption for heating. Hybrid buses fall in the middle, with daily costs ranging from $100 to $250, offering savings compared to diesel buses but falling far short of the cost efficiency of electric buses.”

“Seasonal fluctuations are more pronounced for diesel and hybrid buses, while electric buses demonstrate stable performance throughout the year, demonstrating their economic advantage.”

However, Tian acknowledges that there is a significant barrier to conversion.

“Obviously, these buses are very expensive. Government funding is very important, both for the STM and for users,” she said.

The Flyer XE40 costs around $1 million per unit, while a diesel bus sells for around $750,000.

The STM started purchasing 100 per cent electric buses and its goal is to have an all-electric fleet by 2040 with the purchase of 140 vehicles per year.

This renewal should reduce the STM’s greenhouse gas emissions by 80 per cent in the long term.’

This report by The Canadian Press was first published in French Dec. 7, 2025.

Pierre Saint-Arnaud, The Canadian Press