Allison Transmission launches eGen Flex hybrid system, providing bus fleets with full electric propulsion for zero-emission zones and depot operation
27th August 2020

IndyGo – the Indianapolis Transportation Corporation, Allison and Cummins are partnering to integrate Allison’s new eGen FlexTM electric hybrid propulsion system into three new IndyGo buses.

Allison Transmission, the largest global manufacturer of medium- and heavy-duty fully automatic transmissions and a supplier of commercial vehicle propulsion solutions, including electric hybrid and fully electric propulsion systems, is pleased to announce the launch of its new zero emission vehicle (ZEV)-capable electric hybrid system, the eGen Flex, as the initial product offering under its new Allison eGen brand.

eGen Flex provides bus fleets with full electric engine-off propulsion and accessory power operation capability – ideal for zero-emission zones and depot operation, including when approaching, during, and leaving passenger stops for a quieter and healthier environment. The eGen product family will include Allison’s portfolio of electric hybrid and full electric products, including the company’s portfolio of electric axles.

The eGen Flex electric hybrid system includes an innovative new drive unit, inverter and rechargeable energy storage system. The drive unit includes a disconnect clutch that enables engine-off capability. The inverter has an innovative package improvement that reduces its footprint and weight. The inverter is now water ethylene glycol (WEG) cooled, which eliminates oil lines, decreasing installation complexity, reducing maintenance expense, and increasing uptime. The energy storage system incorporates the latest Lithium Titanate (LTO) technology, which significantly increases energy density, allows for faster charging and enables pure electric (engine off) extended range capability.

With the launch of eGen Flex Allison will offer two distinct models, eGen Flex and eGen Flex Max. eGen Flex will be similar in feature set and capability to the Allison H 40/50 EP electric hybrid propulsion system, but with the package enhancements summarised above. eGen Flex Max will offer fully electric propulsion for up to 10 miles, dependent upon duty cycle and accessory load requirements. eGen Flex and eGen Flex Max will be offered in CertPlus model configurations for sale in California Air Resources Board (CARB)-adopting states. Similar to the existing H 40/50 EP nomenclature, eGen Flex and eGen Flex Max will also be available in “40” and “50” configurations based on fleet torque requirements. Increased Accessory Power 2 will be available with eGen Flex, and will be required with eGen Flex Max. This capability electrifies vehicle accessory systems, such as air conditioning and electric heat, allowing those accessories to operate at their optimal efficiency point, and with clean and quiet electric power, thus reducing emissions and strain on the engine, thereby protecting our environment. Allison is engaged with transit Original Equipment Manufacturers (OEMs) and transit fleets to support a scheduled 2021 commercial release of eGen Flex.

“Allison understands that there is significant interest in electrification,” said Branden Harbin, managing director of global marketing at Allison Transmission. “We also understand that fleets are reluctant to go all in on electrification at this early stage. That critical feedback from our customers is what inspired Allison to deliver this enhanced capability for coach and transit buses, effectively serving as a bridge solution between conventional fuel and full electric solutions. eGen Flex will enable transit fleets to evaluate electric capability and their electric range needs, while still having the peace of mind of a diesel range extender, whether needed for longer routes, for route flexibility, unplanned congestion on routes, or an inability to recharge due to power grid challenges.”

No additional capital infrastructure investment is required to utilise this full electric operation capability. “With the eGen Flex electric hybrid system, Allison continues to build on a foundation of safe, sustainable, and efficient propulsion solutions. We are excited to introduce the eGen Flex propulsion solution as part of our eGen portfolio, providing fleets with an innovative solution that reduces their carbon footprint through an improved emissions profile and reduced fuel consumption.”

IndyGo order

Allison is pleased to announce a partnership with IndyGo, the Indianapolis Transportation Corporation, and Cummins, which will see the eGen FlexTM electric hybrid system integrated into three new IndyGo buses. The eGen Flex Max specified by IndyGo will enable pure electric (engine off) operation for up to 10 miles on any route, at any time, without capital infrastructure investment in charging stations.

IndyGo selected Allison’s H 40 EPTM electric hybrid propulsion solution to power a further 24 new Gillig buses where they will be paired with the industry benchmark Cummins B6.7 diesel engine.

“This partnership with Allison lays the foundation for future collaboration as we jointly advance clean air propulsion and emphasizes our commitment to a clean fleet to improve the greater Indianapolis community and reduce our carbon footprint. IndyGo is in the business of moving people and the decision to choose Allison electric hybrids directly aligns with IndyGo’s mission in providing safe, reliable and accessible mobility options to Marion County,” said Inez Evans, IndyGo President and Chief Executive Officer.

Since 2003, Allison has delivered more than 9,000 electric hybrid propulsion systems globally. These systems have accumulated nearly 2.6 billion miles, saving more than 305 million gallons of fuel, and preventing three 3 million metric tons of carbon dioxide from entering the atmosphere.

Image – The new Allison eGen brand of electric and electric hybrid propulsion solutions positions Allison to lead the charge into the future of commercial vehicle electric propulsion.

Image/Image – IndyGo – the Indianapolis Transportation Corporation, Allison and Cummins are partnering to integrate Allison’s new eGen FlexTM electric hybrid propulsion system into three new IndyGo buses.

About Allison Transmission

Allison Transmission is the world’s largest manufacturer of fully automatic transmissions for medium- and heavy-duty commercial vehicles and medium- and heavy-tactical U.S. defense vehicles, as well as a supplier of commercial vehicle propulsion solutions, including electric hybrid and fully electric propulsion systems. Allison products are used in a wide variety of applications, including on-highway trucks (distribution, refuse, construction, fire and emergency), buses (school, transit and coach), motorhomes, off-highway vehicles and equipment (energy, mining and construction applications) and defense vehicles (wheeled and tracked). Founded in 1915, the company is headquartered in Indianapolis, Indiana, USA. With a market presence in more than 80 countries, Allison has regional headquarters in the Netherlands, China and Brazil with manufacturing facilities in the U.S., Hungary and India. Allison also has approximately 1,500 independent distributor and dealer locations worldwide. For more information, visit