Never lacking daring ideas, billionaire entrepreneur Elon Musk is determined to jolt the electricity market. The CEO of electric car maker Tesla Motors hopes to park hundreds of millions of large, solar panel-connected batteries in homes and businesses so the world can disconnect from power plants—and he can profit. On Thursday night, before an adoring crowd and a party-like atmosphere, Musk unveiled how he intends to do it. Musk took the stage at Tesla's design studio near Los Angeles International Airport, an audience of drink-toting enthusiasts cheering him on, in a scene fitting for an audacious dreamer renowned for pursuing...