eGen Flex®

eGen Flex® electric hybrid provides revolutionary capabilities and fully electric propulsion for up to 50% of route depending upon duty-cycle, without the added infrastructure requirements of full EV. Our advanced technology provides a fully electric mode with geofencing capabilities when entering zero-emission zones or depots, reducing emissions and noise levels, specifically in highly populated areas.

A blue and green transit IndyGo bus with


“After eight months in use, IndyGo is very pleased with the flexibility Allison Transmission’s eGen Flex buses offer, allowing us to reduce our carbon footprint in some of the most densely populated, high-air pollution pockets of our city. This technology represents the next step in our efforts to reduce our dependence on fossil fuels, enhance quality of life for residents and do our part to protect the environment.”


- Inez Evans, IndyGo President and CEO


  • Drive Unit

  • Inverter

  • Rechargeable Energy Storage System


Drive Unit White navigation arrow

  • Multispeed gearbox
  • Fully integrated electric motors built into the gearbox
  • Same proven industry-leading reliability
  • Disconnect clutch added to enable disengaging input shaft from the engine
  • Provides propulsion while the engine is at zero speed, enabling full engine-off propulsion capability

Inverter White navigation arrow

  • Improved efficiency
  • Improved packaging – one-third the weight and half the footprint than inverter used in earlier generation electric hybrid systems
  • WEG cooling – no oil-coolant lines from the drive unit, reducing installation complexity and maintenance costs

Rechargeable Energy Storage System White navigation arrow

  • Lithium Titanate (LTO) chemistry ideal for electric hybrid operation with constant recharging
  • Increased energy capacity – industry-leading 10-mile electric range capability
  • Battery design life of eight years
  • Faster charging than other chemistries
  • Improved fuel economy up to 25% versus conventional diesel buses
  • Operate accessories such as air conditioning and heat at their optimal efficiency with clean and quiet electric power
  • No new charging infrastructure required
  • No engine emissions or noise in dense pedestrian areas while loading and unloading passengers 
  • Electric vehicle operation in zero emission zones and bus depots with geofencing capability
  • Up to 50% of route in electric range, duty-cycle and axle-ratio dependent
  • Reduced CO2 emissions
  • Eliminate inefficient belt-driven accessories and reduce the load on the engine
  • Reduced brake wear and increased power through electric hybrid regenerative braking
  • Inverter utilizes WEG cooling, eliminating oil coolant lines from the drive unit, reducing installation complexity and maintenance costs

Reduce Dependence on Fossil Fuels at the Pump

Enhance Quality of Life

Protect the Environment

Reduce Downtime and Maintenance Costs

Innovation that Drives

If you would like more information on our eGen™ family of products or to stay informed about our latest innovations, please use this form to get connected. You’ll receive a confirmation email containing our latest product brochures.