"That means a 333-horsepower supercharged V-6 from the Audi S4 and a 47-horsepower electric motor can be found underhood, paired by a decoupling clutch to allow each to run independently.
The Cayenne S Hybrid features a ‘hybrid controller’ system that coordinates the two drive units through the center clutch, enabling the SUV to be driven up to nearly 40 mph on electric power alone. As we mentioned in our First Drive article, the Cayenne S Hybrid can also coast on the freeway at speeds up to 86 mph using only electric power. The Porsche’s infotainment display monitors power usage and alerts the driver as to which mode the Cayenne is running in — combined gas/electric, or one of those two alone."
@ http://www.automobilemag.com/green/news/1003_2011_porsche_cayenne_s_hybrid/index.html