Tesla Motors CEO Elon Musk on Wednesday unveiled a far-reaching “master plan” for the electric automaker that envisions self-driving semis and buses — and a car-sharing service to rival Uber. Rather than focus on spreading the popularity of electric vehicles, Tesla now aims to change the way society generates, stores and uses electricity. Even though the Palo Alto company currently builds just two lines of cars — the Model S sedan and the Model X SUV — and has struggled this year to meet production goals, Musk made clear Wednesday that Tesla wants to tackle nearly every major category of road transportation. [...] with its planned acquisition of San Mateo’s SolarCity, Tesla will offer rooftop solar arrays to generate the electricity for its batteries and cars. “The point of all this was, and remains, accelerating the advent of sustainable energy, so that we can imagine far into the future and life is still good,” Musk wrote in the plan, posted Wednesday evening on Tesla’s official blog. In addition to the $35,000 Model 3 that Tesla plans to introduce next year, the company is developing a pickup truck, a heavy-duty “Tesla Semi” and a “high passenger-density urban transport” that could replace traditional buses. “This dramatically lowers the true cost of ownership to the point where almost anyone could own a Tesla,” Musk wrote. Since most cars are only in use by their owner for 5 percent to 10 percent of the day, the fundamental economic utility of a true self-driving car is likely to be several times that of a car which is not.