ISE's standard hybrid drive system uses electrically-driven power steering, braking, and heating, ventilation, and air conditioning accessories. These subsystems derive power from the main battery pack when the APU is not running, so there is no loss of functionality when the bus operates in its all-electric mode. The electric accessories also enable more efficient operation of the power steering, power braking, and heating/ventilation/air conditioning (HVAC) systems.

We estimate that this reduces aggregate power demands on the drive system by at least 15 horsepower, which is a substantial percentage of the average power consumption of a bus during local driving, when average power for locomotion is typically no more than 50-70 Hp. ISE has also developed a higher power accessory system that enables electric operation of the lifting and compacting mechanisms on large refuse trucks. Electrical operation of these systems allows refuse trucks to operate much more quietly, as well as improving energy efficiency and reducing emissions.

By allowing the engine/APU to be completely shut down for extended periods, the electrically-drive  accessory subsystem helps reduce fuel consumption and emissions, and enhances overall vehicle operating efficiency. This also enables ultra-quit, zero emissions vehicle operation in noise sensitive or environmentally sensitive areas.