Does Tesla, the maker of electric cars and battery storage, mesh well with SolarCity, which installs solar power systems? Elon Musk, who helped found the two companies and heads them as chairman, is convinced that their destinies are tied together as “the world’s only vertically integrated sustainable energy company.” Musk first aired his thoughts on June 21, and Tesla announced the $2.6 billion merger on Monday to mixed reactions. Some saw synergies in the customer profiles of the two companies and cost savings. But skeptics felt Musk may not have the bandwidth to accommodate a merger while Tesla races to deliver its Model 3 car in 2017 and grapples with safety concerns over driverless technology after one if its cars was involved in a fatal accident. Tesla said it expects to achieve cost synergies of $150 million in the first full year after closing; it expects the merger to close in the fourth quarter of this year.…