Adrian Newey has admitted KERS is "a headache" for Red Bull.
It is believed some of the problems experienced by Mark Webber in Saturday's third practice in Shanghai before qualifying were caused by his energy-recovery system malfunctioning.
On the otherwise-dominant RB7 car, then, KERS has been described by commentator's as Red Bull's Achilles Heel in 2011.
"The integration of KERS with the other systems is the biggest problem," admitted car designer Newey, who is no fan of the technology but resigned to its performance advantage this season.
He said it has been a challenge to package KERS whilst minimising "the impact on the aerodynamics".
"For an independent team like us it is a headache. Our KERS is based on the KERS system of 2009," Newey is quoted by laola1.at.