Regenerative braking allows a car to absorb kinetic energy during braking and release that energy during acceleration or hill climbing, reducing fuel consumption. This technique also takes most of the load off mechanical brakes, reducing brake maintenance and replacement expenses. In electric and hybrid vehicles, the power density of lithium-ion battery technology is often inadequate compared to the superior power output of ultracapacitors.

Start-stop applications enable the engine to shut down when it comes to a stop at a red light or when sitting in traffic. Ultracapacitors then provide a short burst of energy that restarts the motor. This technique delivers significant savings on fuel and reduces emissions. It is expected that start-stop systems will become the most cost effective way for automakers to pursue higher fuel efficiencies targets and that as many as half of new cars will be fitted with them by 2022.