Why donate time and computing processes for cancer research through the World Community Grid project, of course.

ENGADGET: Wind tunnel PC case pushes the air cooling envelope, does its thing for cancer research

But, of course, grid emissions vary widely, and the Volt would be much cleaner in California than in, say, coal-heavy Indiana.

FORBES: Green car book disses the Chevy Volt, GM isn't too happy

And, of course, the grid is continually getting cleaner, so electric vehicle scores will improve.

FORBES: Electric Cars Aren't Green, Says Ph.D.

Of course, more distributed generators contributing variable renewable energy to the grid means an increasing challenge to regulate the consistency of supply and demand.

FORBES: Distributed Generation: Key Part of Our Energy Future - Phil Harris