We knew winter was hard—now we know how hard

As cities worldwide transition to electric public transportation, new research from Cornell University highlights a significant hurdle: cold weather.

An articulated bus on Line 300 stands at a snowy stop between Amsterdam Arena and Haarlem via Schiphol. These 21-meter models, with capacity for 180 passengers and running every 6 minutes, were introduced in winter 2017. They were replaced in 2020 by 18-meter electric buses better suited for efficiency and cold-weather operation. Photo: Kristian Köhntopp, Flickr CC BY-SA 2.0

As cities worldwide transition to electric public transportation, a new study from Cornell University highlights a significant challenge: cold weather. The research, focusing on electric buses operated by Tompkins Consolidated Area Transit (TCAT) in Ithaca, New York, reveals that low temperatures substantially increase energy consumption, posing challenges for fleet reliability in colder climates.

The Cornell University study adds important new insights and real-world validation to what was previously understood about electric buses and cold weather. Here's what’s new and notable:

What was already known

• Cold temperatures reduce EV battery performance due to slower chemical reactions and increased internal resistance.

• Cabin heating is energy-intensive, drawing from the same battery that powers the vehicle.

• Regenerative braking and range drop significantly in sub-zero temperatures.

• Transit agencies in Nordic countries and northern U.S. states have reported cold-weather operational issues for years.

What’s wew in the Cornell study

1. Precise quantification of energy loss

Cornell's study offers detailed, statistically backed real-world data:

• 48% more energy used when buses operate between 25°F and 32°F.

• 27% increase in energy use across the broader 10°F to 50°F range.

• This is one of the first peer-reviewed studies based on U.S. public transit data (from TCAT in Ithaca, NY), not just lab or model-based simulations.
  

2. Operational detail from actual bus routes

Unlike previous studies relying on modeling or simulations, Cornell analyzed daily operations, including:

• Impacts from frequent door openings (heat loss).

• Inconsistencies in battery thermal management during real-world regenerative braking.

• Seasonal variability in charging performance and route completion.
  

3. Emphasis on driver behavior and depot strategy

The study makes practical recommendations, including:

• Driver training to reduce open-door time and unnecessary idling.

• Charging while batteries are still warm, not after cooling down.

• Heated indoor storage to maintain thermal conditions overnight—rarely highlighted in earlier studies.
  

4. Direct implications for fleet planning

The research connects energy loss to fleet-level impacts:

• Reduced range leads to more charging time and fewer completed trips.

• Potential need for more buses or altered schedules in winter months—adding cost and complexity.

The Cornell study doesn't reinvent what we know—it confirms, deepens, and quantifies it with real-world, route-specific data. That’s crucial for transit agencies planning large-scale electric rollouts, especially in temperate or cold regions. It shifts the conversation from «cold might be a problem» to “here’s exactly how much of a problem it is—and how we can mitigate it.”

Broader context

These findings align with experiences in other cold regions. For instance, Chicago's Transit Authority has implemented fast-charging stations and auxiliary diesel heaters to mitigate cold weather impacts on their electric buses.

In Oslo, Norway, extreme cold led to the temporary withdrawal of several electric buses from service, highlighting the need for robust cold-weather strategies.

Recommendations

To enhance electric bus performance in cold climates, the study suggests:

• Indoor storage: Keeping buses in heated facilities to maintain battery temperatures.

• Optimized charging: Charging batteries while they are still warm to improve efficiency.

• Driver training: Educating operators on minimizing door-open times and other practices to conserve energy.

As municipalities aim for sustainable transportation solutions, addressing these cold-weather challenges is crucial for the reliable operation of electric bus fleets.

New generation of batteries?

Hope may be on the horizon. Battery makers and researchers are fast-tracking the development of next-generation batteries designed to withstand cold climates. Several promising technologies are under review:

1. Solid-State batteries

Unlike current lithium-ion batteries, which use liquid electrolytes that freeze or become sluggish in cold, solid-state batteries rely on ceramic or glass-based materials. These can maintain conductivity at much lower temperatures, offering improved cold-weather performance, safety, and energy density.

Companies like Toyota, CATL, and QuantumScape are expected to debut early commercial models between 2025 and 2027.

2. Thermally adaptive battery packs

Some manufacturers are experimenting with thermo-regulated enclosures that pre-heat battery cells using residual energy from braking systems or solar-assisted panels. This would help maintain optimal temperature during idle periods and extend operational range without drawing more power from the battery.

3. Lithium-Titanate (LTO) Cells

While not new, LTO batteries offer excellent low-temperature performance and ultra-fast charging. However, their lower energy density has been a trade-off. With new materials being tested, LTO 2.0 cells may soon overcome this limitation, making them a viable option for urban bus networks.