Electric and hybrid solutions

Completely electrifying bus power and propulsion in a hybrid system

Series-E & ER

Transit bus systems around the globe are driving into the future with BAE Systems’ advanced Series-E & ER electric hybrid bus propulsion systems.

Our Series-E & ER smart electric drive propulsion systems power your buses completely electrically, and even operate in zero emissions mode. That gives transit systems a healthy edge in achieving energy efficiency and clean air goals.

More than 12,000 of our electric drive bus systems now operate around the globe, providing power for both electric bus accessories and electric propulsion. BAE Systems offers two electric drive solutions — the Series-E and the Series-ER – to provide low emission operations. The electric motors drive the wheels and associated power electronics are designed to power all vehicle accessories. The only difference is the energy storage systems.

The Series-E system

The Series-E system is transit's cost-effective green solution providing engine-off technology with a lower total cost of ownership. With our smart Series-E drivetrain technology in your buses, all of your bus accessories – air conditioning, power steering, air compressors, etc. – can be powered by our electric system, and our stop/start function can be used to decrease engine idling at stops. Furthermore, the combustion engine that keeps the batteries charged can be shut-off for short distances – in and around a bus depot or hotel stop, for example – to eliminate emissions and reduce noise.

Series-E's uses our ESS-3G-1K energy storage system which uses long-life ultra capacitor technology. With more than 500 ESS-3G-1K systems in service and a minimum 12-year life Series-E is an excellent towards battery electric solutions. All of our system components are common and a low emission vehicle today can be upgraded to a full zero emission battery electric solution when ready.

The Series-ER system

For more "engine-off" electric bus time, you want the Series-ER. Its higher capacity energy storage system, ESS-3G-32K allows drivers to operate the bus up to 35% of the time with the engine off, increasing low and zero emission travel options. Recently, San Francisco Municipal Transportation Agency (SFMTA) set up zero-emission zones or green zones using Series-ER paired with geofencing technology. The green zones — nine in total — are located in population-dense neighborhoods most affected by air pollution. Each of the zones have a large presence of traffic that is contributing to a high rate of air pollution. Another advantage is that Series-ER can also be implemented without high infrastructure costs. This system has an onboard generator, so San Francisco– and your city – can operate electric drive buses without needing to install charging infrastructure and without scheduling times for buses to stop and recharge. With Series-ER installed, once the bus drives out of the geofenced area, it will automatically switch back into electric-hybrid mode.

Series-ER is transit's low-risk path to full battery electric drive. Using common components operators can transition from Series-ER: electric range solution to our highly-efficient Series-EV: battery electric system.

Complete Integration & Support

BAE Systems provides our customers with the most comprehensive power and propulsion systems integration and support in the industry. While others often just ship their system parts to prime bus manufacturers to install, we've sent a certified Application Engineer along with our cutting edge power systems to make sure they are integrated properly from day one, including on-site technical advice and thorough training. Then we back that work with our Flexible Service Plan – customized to fit the customer's business model – including a coordinated spares management program.


Learn more. Visit our electric hybrid bus, electric bus, hydrogen fuel cell electric, and other transit bus power systems pages below. Download our Get To Zero brochure. Or contact our electric and hybrid solutions director of business development today to arrange a meeting.

Electric and hybrid solutions

See Product Family