Where Kennedy will ultimately fit into all of this remains to be seen. He told me: “We don’t need missionaries anymore. We need mercenaries.” As the industry grows, big investments don’t necessarily flow toward the people with the deepest environmentalist roots. No matter how much orange Kennedy wears or how dedicated to corporate branding he appears to be, his bleeding heart still shows through. Missionary, mercenary: can he — can anyone — be both?

Of the residential solar-power companies with national aspirations, Sungevity is among the smallest in terms of market share. Sunrun, one of the market leaders, is led by Lynn Jurich and Edward Fenster, two Stanford Business School graduates who got into the business, as Jurich told me, in part because “the numbers worked.” SolarCity, another market leader, was founded by the brothers Lyndon and Peter Rive; Lyndon had previously founded Everdream, a software company that was eventually bought by Dell. The venture is also backed by Elon Musk, the Rives’ cousin and more notably a founder of PayPal; Tesla, the electric-car manufacturer; and SpaceX, a private space-exploration company. In 2004, Lyndon Rive was in a car with Musk on the way to Burning Man in Black Rock Desert, Nev., when the idea of getting into the solar business first hit him. (SolarCity also has a commercial solar-power business and is planning an initial public offering later this year, which could value the company at $1.5 billion.) Another company, SunPower, which is also a solar-panel manufacturer, does a big business in the residential market in California, through its dealer network. Kennedy and Sungevity run, roughly, fourth in California — which, because it’s the biggest market, most of these companies view as a proxy for the rest of the nation. But because of Kennedy’s background with Greenpeace, his big Australian personality (he was born in the United States but identifies as, and sounds like, an Australian) and some of his high-profile connections, he and Sungevity have received a fair amount of media attention. The actress Cate Blanchett was an early investor, and the actor Mark Ruffalo recently began leasing a system from the company, which he discussed in an appearance on “The Colbert Report” in March.

This clearly rankles Kennedy’s competitors. John Ordona, the director of communications at Sungevity, interviewed with another large solar company before taking the job at Sungevity. “They basically said that Danny was a tree-hugger and that Sungevity had no real business plan,” he told me. When I visited Sunrun, I was shown a graph indicating the size of their lead in California. When I asked about Kennedy and Sungevity directly, I was told by a marketing person, through a tight smile, “Their mind share is bigger than their market share.”

Compared with the relatively smooth and recent road that some of his competitors took to arrive at the business of residential solar-power installation, Kennedy’s path has been unusual. He has been fighting against oil and coal for most of his adult life. He got his start as an environmental activist at age 12, when he fought, as part of a landmark victory for conservationists in Australia, against the construction of a dam in Tasmania. After attending college, he worked for Greenpeace in Papua New Guinea, where he observed the efforts of villages to resist exploitation by international oil companies. There, in 1993, he nearly died after contracting malaria while trying to document the environmental damage Chevron was causing in the region. He was saved only after villagers rowed him, delirious with fever, upriver in a dugout canoe to the secluded home of a young Japanese anthropologist who happened to have a rescue agreement with Chevron. She lighted a signal fire, releasing a plume of colored smoke, and within hours a small helicopter airlifted Kennedy to Chevron’s base camp, where an American doctor administered the drugs that saved his life. Once he was on the mend, Kennedy left Chevron’s base camp and went right back to his efforts to expose the actions of the company that had just rescued him. “I stayed out in the field and continued to work,” he says. “Went back to the village and told them, ‘Everything’s cool, thank you very much for getting me out of there.’ ”

Kennedy left Greenpeace in 1995 and the next year founded Project Underground, which could be more flexible than Greenpeace and was more narrowly focused on issues of social justice and human rights. A year later, he was detained for three days by Indonesian intelligence. He suspected that a courier reported him for trying to ship water samples abroad — water samples that would demonstrate the environmental abuses at the enormous Grasberg gold mine in Irian Jaya. These were the days of Suharto’s repressive regime, and Kennedy says intelligence officials deprived him of sleep and forced him to dictate his version of events over and over again. At one point, he said, they threw him into a jeep and drove him to an old prison complex, where they told him to get out and walk around, despite a tropical thunderstorm. As he got out of the car and felt the men’s eyes on his back, he assessed his chances of running for the forest line and escaping somehow. He thought they might try to shoot him. Instead, they loaded him back into the car, took him back to the cell and asked for his statement again. “Messing with my head,” Kennedy says.