Tesla Motors chief Elon Musk revealed the second part of his master plan for the electric automaker and solar company.  He wants to branch out into buses and trucks, while the solar power division would develop solar roofs with battery storage.

"We must at some point achieve a sustainable energy economy or we will run out of fossil fuels to burn and civilization will collapse," Mr. Musk said at an event in San Francisco this week to announce his "Master Plan - Part Deux".  "Given that we must get off fossil fuels anyway and that virtually all scientists agree that dramatically increasing atmospheric and oceanic carbon levels is insane, the faster we achieve sustainability, the better."

The expansion plans are the second half of the vision he laid out when Tesla Motors started out.  Since then, the company has produced well-reviewed but pricey electric cars with advanced features.  The company has fallen behind schedule in delivering a more affordable consumer choice, but Tesla is already expanding its horizons into solar energy with the planned acquisition of the Solar City company.

Still, some critics think it's overly ambitious.

"As is typical, Elon Musk has laid out a grandiose plan for the future with no time frames and few specifics and no mention of how and when Tesla will be profitable," said Autotrader senior analyst Michelle Krebs.  "Tesla's latest Master includes expanding its electric vehicle product line to cover all major segments when it hasn't been meeting production targets with the limited product line it has now and in the next couple of years."