[MetroMPG]

GM considers stereo draw significant enough to have given BOSE the task of improving unit efficiency for use in the Volt:

So the Bose folks were challenged to come up with a new sound system that cranks heavy tunes with a light touch, putting out a big sound from a small space. The result? The Volt’s Bose Energy Efficient sound system will be 30% smaller, 40% lighter and, most importantly, use 50% less energy than a comparable existing system. It’s like removing 50 pounds from the car’s weight. When trying to reach 100 mpg, every pound counts.

Source: GM to Volt Suppliers: Get Us 100 MPG | Hybrid Cars