Electric Hybrid Propulsion for Transit Buses


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Electrify Your Fleet with Allison's Revolutionary Electric Hybrid

Allison Transmission is leading the charge in innovative propulsion solutions. The eGen Flex®electric hybrid provides revolutionary capabilities and fully electric propulsion when you need it, without the added infrastructure requirements of full EV. Our electric hybrid systems continue to demonstrate bottom-line operating benefits for municipalities and fleets all over the world while delivering industry-leading performance, reliability and durability.

Proven Electric Hybrid Solutions

These approximate figures represent the eGen Flex's impact around the globe, as of 2024.

units
cities worldwide
accumulated miles
gallons of fuel saved

Inside eGen Flex®

A product render of the eGen Flex drive unit.

Drive Unit

Featuring a multispeed gearbox with fully integrated electric motors built in, the drive unit provides propulsion while the engine is at zero speed, enabling full engine-off propulsion capability.

A product render of the eGen Flex inverter.

Inverter

Designed to improve vehicle efficiency and save space, Allison reduced the inverter to be one-third the weight and half the footprint of earlier generation electric hybrid systems.

A product render of the eGen Flex Rechargeable Energy Storage System

Rechargeable Energy Storage System

eGen Flex® uses lithium-titanate (LTO) battery chemistry to support EV operation. The electric battery is recharged through a regenerative braking system, enabling storage of energy caused by the friction from braking that would normally be released as heat.

eGen Flex® Highlights

Reduced Dependence on Fossil Fuels

Fleets that operate eGen Flex® can expect improved fuel economy of up to 25% compared to conventional diesel buses. The system’s electric battery is recharged through a regenerative braking system, eliminating the need for charging infrastructure. It also allows the vehicle to operate accessories, such as air conditioning and heat, at optimal efficiency with clean and quiet electric power. 

Increased Vehicle Uptime

eGen Flex® eliminates inefficient belt-driven accessories and decreases the load on the engine. The regenerative braking system reduces brake wear and increases power to the wheels. In addition, the inverter utilizes WEG cooling, eliminating oil coolant lines from the drive unit. These factors all contribute to reduced costs for vehicle integration and maintenance.

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Protecting the Environment

The system’s electric-only mode enables buses to operate in full EV mode using geofencing technology. This helps fleets reduce their carbon footprint and noise pollution, particularly in pedestrian-dense EV zones.

Allison eGen Flex® in Action

New Orleans RTA Selects Allison eGen Flex®-Equipped New Flyer Electric Hybrid Buses

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A product render of the three components of the Allison eGen Flex: the drive unit, the inverter and the RESS

Allison Transmission and B-Metro Partner on Electric Hybrid Technology to Modernize Public Transit System in Texas

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A photo of an IndyGo bus with the Allison eGen Flex logo on it.

IndyGo Partners with Allison Transmission to Expand Electric Hybrid Fleet in Indianapolis

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See All eGen Flex® News

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