Within 12 hours of meeting Lyndon Rive, I was in the San Mateo Medical Center’s emergency room, right eye swelled shut, spine supported by a neck brace, blood seeping from the side of my face. The cause of trauma: an evening mountain bike ride with Lyndon Rive. The perfect way to unwind after work, he’d assured me. Unfortunately, we hadn’t discussed our relative ideas of relaxation. Minutes into the ride, while Rive was gleefully careening down the precipitous rocky trail, I was flying over the front of my handlebars. Thankfully, someone from Rive’s office had supplied me with safety glasses beforehand (which may well have saved my cheekbone and eye socket, a doctor told me later). Over the years, apparently Rive’s comrades have grown accustomed to this sort of thing.

I hadn’t traveled to Menlo Park, California, to mountain bike. I was there to talk to the 39-year-old entrepreneur about the company he co-founded and runs — SolarCity, America’s leading residential solar company. Since launching in 2006, it has raised billions of dollars and installed hundreds of thousands of home solar systems, more than anyone in America. But lately SolarCity is in deep trouble. Customers aren’t signing up in the numbers they did two years ago, back when oil was trading at more than $100 a barrel. U.S. lawmakers are investigating the company’s financial practices. Earlier this year, in the span of two months, the company’s stock lost 70 percent of its value.

Most recently came the announcement that SolarCity would be acquired by Tesla, the electric-car company founded by Elon Musk, for $2.6 billion in stock, a move largely decried on Wall Street as a nepotistic bailout. The finance types were suspicious because in addition to being Tesla’s founder, Musk is also SolarCity’s chairman and largest shareholder — as well as Rive’s first cousin.

What is it like to be Rive at this moment, I wondered. Here he is, an ambitious and driven CEO, fighting for the life of his company. If he prevails, SolarCity will be a global power giant based entirely on clean energy, and he’ll be celebrated as the guy who brought cheap solar power to the masses. Yet even then, his achievements will be overshadowed by his cousin Elon’s, a man widely touted as the greatest entrepreneur of his time, whom Rive has admired and sought to please ever since they grew up together in South Africa. How does a man cope with that kind of pressure?

Rive always makes time for cycling. It’s part of how he manages his stress. So after 6 p.m., we met up at a little house he owns near a trail in nearby Belmont. He’d already changed out of his chinos and SolarCity polo shirt and into bike shorts and a SolarCity technical shirt. His office had delivered his Specialized Stumpjumper and an Enduro for me. As we mounted up, his eyes were bright, his smile wide: Let’s crush this. Ten minutes later, Rive was killing it and I was hurtling ditchward.

I had learned the first rule of Rive: You can get hurt trying to keep pace with the man. It turned out that I had joined a dubious fraternity. His chief financial officer, a serious rugby player back in France, tore up his leg on the very same bike trail. Other SolarCity executives have crashed while skiing tree runs behind their boss at Lake Tahoe. Rive also finds time to kitesurf and play on the U.S. national team for underwater hockey, a sport that sounds ridiculous but is actually physically grueling and strategically mind-bending.

His days at SolarCity are intense in a different way. The company, in fact, could be one of the most risk-laden in operation today. To install solar systems across 27 states and Mexico, SolarCity takes on gobs and gobs of debt — billions of dollars a year. The eventual goal is to create a massive network of home solar systems. The problem is, if customers stop paying their SolarCity energy bills or investors stop lending, the company will blow up like the subprime housing bubble.

“We have to get off fossil fuels, and I don’t think there’s any way you could do it differently,” Rive told me. SolarCity’s grid can produce as much as 8 million kilowatt-hours in a day, enough to power more than 267,000 homes, energy that would otherwise require burning 4,160 tons of coal. “If we don’t do it, who does it?” he said. “There is no one. There is no one pushing transformation at this level.”

Despite the stakes — or perhaps because of them — Rive says he’s in his element. “When things are going good, I feel, like, this is boring. When things are rough and you’ve got to focus on the business, that’s fun.” That’s the second rule of Rive: To his family, fear is not a deterrent and risk is a type of fuel.

The trip to the emergency room was my first real chance to chat with Rive, who had offered to drive me over. He took the wheel of my rental Hyundai Sonata and slid back the driver’s seat to accommodate his 6-foot-2 frame as I eased into the passenger side, a hand towel pressed against the side of my face to keep bloodstains off the upholstery. I decided to use my head wound as a conversation starter: What were his worst injuries? He smiled, shrugged, seemingly reluctant to reply. “Huh,” he said with the slight honk of a South African accent. “I’d say I’ve been pretty fortunate.” There’d been two motorcycle accidents — as a teenager, he’d smashed his whole leg while flying over the top of a car that had cut him off. “But I came out pretty undamaged,” Rive said. He changed the subject to his sister, a competitive dirt bike rider. “She’s wrapped herself around trees,” he said, almost abashed that he had mentioned his comparatively minor shattered leg.

Once I was safely squared away with medical staff at the hospital, Rive rushed off. He had several more hours of work that night, ahead of the following day’s board meetings.

No one in Rive’s family works a normal 9-to-5. The seven children of Rive’s mother, Almeda, and her twin sister, Maye, have gone on to become independent filmmakers, restaurateurs, rocketeers. In 1952, years before Rive was born, his grandmother and grandfather became the first amateur pilots to fly a single-engine plane from Africa to Australia. Rive’s mother, now 68 and living in Calgary, Alberta, remembers family expeditions to uncharted regions of the Kalahari Desert, spending nights amid lions and hyenas. “Africans would tell us they’d bite our faces off when we were sleeping,” she told me.

Rive may not be facing hungry hyenas, but the business climate at SolarCity these days can seem just as vicious, with sniping short sellers, stubbornly expensive operational costs, and lawsuits. Jim Chanos, the billionaire hedge-fund investor who is most famous for betting against Enron, has said that SolarCity’s business likely is doomed. “The problem with SolarCity is they’re losing money on every installation and making it up in volume,” Chanos told CNBC in May. Meanwhile, in Congress, Senators Jeff Flake and John McCain have launched an investigation to find out whether SolarCity is juicing its numbers — overstating the cost of its solar systems in order to get bigger tax credits and cover the spread. When Musk announced that Tesla was acquiring SolarCity, observers on Wall Street wondered if the latter company was already in danger of missing debt payments. All that doubt damages the faith of investors, whose money SolarCity desperately needs to keep going. Even for a Rive or a Musk, it’s enough to set the heart racing.

“Fuck yeah, it’s stressful,” says Peter Rive, one of Rive’s two older brothers and a SolarCity co-founder. “That’s why we mountain bike and kitesurf and hang out with family,” he told me. “You try to get out in nature and do sports. It’s a great way to vent. If you’re doing a big climb together, you’re constantly talking about work — you talk through the stress.”

The Rives grew up in a sprawling house in an upscale neighborhood of Pretoria, a city of 700,000 in the north of South Africa. The home doubled as their mother’s holistic health institute. When the kids were growing up, she had a rule: No giving up. That’s why Lyndon Rive attained a brown belt even though he was sick of karate by the time he had a yellow. She also had a motto: “Business must always come first.” It was common for her to work from 7 in the morning until 11 at night, with only a few breaks to take care of the children (a nanny tended to them the rest of the time). When her children turned nine, she enlisted them to distribute flyers for the business. If the office phone rang, the children were to be quiet immediately. Even today Almeda Rive says proudly that Lyndon instinctually respects the rule when she speaks with him. “If the phone goes in the middle of the sentence, he’ll just go quiet,” she said.

Growing up, Rive struggled with reading and spelling; these days he would likely be classified as dyslexic, his mother believes. Determined to help him succeed, she set aside two hours every afternoon for tutoring. When he turned 14, she began holding “business meetings” with him every week, where he presented an idea for a new business and they would discuss it.

Rive’s older brothers, Russ and Peter, hung out with their cousin Elon, who lived nearby, often engaging in entrepreneurial exploits. One year they sold chocolate Easter eggs to their parents’ friends; later they almost signed a lease on a retail space to build a video arcade near school. Lyndon, the youngest of the brood, tended to be excluded, too small to join in. But he was determined to compete. He started playing underwater hockey because his older brother Peter had taken up the sport. As a teenager he practiced constantly in the pool of his then-girlfriend and now wife, Madeline. By the time Lyndon was 20, Peter had long moved on, but Lyndon and Madeline had both made South Africa’s national underwater hockey teams. “He always thought he was equal to his brothers,” said Almeda. “I would tell him he was much younger than his brothers, but he wanted to be in charge.”

Rive barely graduated from high school. By then he was focused on one of the ideas he’d developed in his mother’s business meetings: a line of homeopathic medicines (lavender cream for arthritis; an ointment for muscle stiffness) that he distributed through her institute and other locations. “The principal wanted to expel me, but then I showed him my financials,” Rive says. Says Almeda: “He was making better money than the teachers.”

In 1998, Rive and Madeline traveled from South Africa to the Bay Area to compete in that year’s underwater hockey world championships. They stayed with Musk, who had been in Silicon Valley since 1994 and was already at work on his first startup, a Web software company called Zip2. Rive fell in love with the promise of California and convinced his brother Russ to move to the Valley. In 1998, with the tech boom in full swing, the brothers started a company called Everdream, which offered an early version of IT software that allowed tech-support staff to access computers remotely to fix problems. Musk pitched in, extending advice and giving Rive and Madeline his old San Francisco apartment to live in.

The idea for SolarCity grew out of a road trip the cousins took to Burning Man in 2004. Musk had fronted the money for the RV and let his cousin and his wife take the master bed. As the trio drove to Black Rock Desert, Rive told Musk he was getting bored with selling small-business software. He wanted to do something bigger, something that might impact the world. Musk told him that solar power was a no-brainer. The world would have to get off fossil fuels — if not to prevent global warming then because oil, coal, and gas were finite and expensive resources. Bringing down the costs and pricing solar the same as fossil fuels would be a tipping point. The whole world would go solar. If they started now, they might rule the market.

On July 4, 2006, SolarCity launched with Lyndon as CEO, Peter as chief technology officer, and Elon putting up the majority of the original $10 million investment and acting as chairman. Their original plan was modest, akin to a renewable-energy Groupon: They asked customers to rally their neighbors; if enough of them signed up, SolarCity would negotiate a 30 percent discount for the panels and install them. But few neighborhoods had the motivation or the cash to go solar en masse. So in 2008, SolarCity switched to the no-money-down model, where anyone with a sunlit home and a decent credit score could get a solar system installed. Thanks to rising oil prices and generous federal tax credits, they offered lower prices than most conventional utilities, and customers flocked to SolarCity. In the next six years, the company expanded operations to 21 states.

As they built solar systems on one rooftop after another, they also burned through more and more cash. To attract more lenders, the company packaged and resold the debt to banks as complex bonds and other financial products that handed the financiers shares of SolarCity’s tax credits. The business became a whirlwind of signing up solar customers, followed by endless investor meetings. Rive’s life became more and more frenetic.

By this time the Rives had two small boys (they’re now seven and eight). Madeline grew concerned that Rive was missing out on spending time with his children, and her. She had long known the Rive philosophy, “Business must always come first. But when the boys could speak and ask where Daddy was and why he wasn’t there, that was when I pulled him in and said, ‘Let’s talk about it,’ ” she told me. “And he listens. He can listen.”

Rather than relax, Rive solved the problem in a classically Musk-Rive–ian way: He reengineered his work-life balance. He picked what he thought was the optimal number of weekly quality-time hours with his children — 16 hours — and instructed Nikki Marasco, his assistant, to build that time into his calendar and work backward. Then he reclaimed the time elsewhere. Instead of driving himself, he now uses Uber so he can work on his laptop in the backseat. Rather than long sessions at the gym, he gets out of bed, walks a few feet to a treadmill, and sprints — the most time-efficient way to get in his cardio. Then he walks another few feet to the shower. He has standardized his breakfast so he doesn’t waste time with that meal, either. Hence, a kale, spinach, blueberry, banana, celery, and cucumber concoction known in the company cafeteria as “the Lyndon,” which he consumes three times a day. Nothing is untenable or impossible — it’s just a logic puzzle to be solved.

The day after my bike wreck, after a full day of board meetings, Rive meets me at the Burgess Pool in Menlo Park for the U.S. national team’s underwater hockey practice. I’m supposed to participate, but I’m in a neck brace and my right eyebrow has 13 stitches, and I’ve got a chipped bone in my neck.

Rive isn’t practicing tonight either. Too much work for tomorrow’s meetings, he says, but he wants to show me the sport. We stand at the pool’s edge and peer down. It’s after sunset. The underwater lights glow a ghostly blue. Beneath us, human bodies writhe and chase one another like eels. Other than the occasional splash of a surfacing player, it’s quiet. It’s hard to make out what’s happening.

“In the water it’s much better,” Rive says. “It’s probably one of the reasons people don’t know about it.”

Here’s what I gathered: Just as in ice hockey, underwater hockey players push a rubber puck into a goal with a stick, except the sticks are flat plastic batons the size of paint stirrers, and the players are clad in fins and masks. There are six players on each side, not five, and games comprise two halves of between eight and 15 minutes, depending on the tournament. The game, originally known as Octopush, was started in 1954 in England by a group of deep-sea divers looking for subaquatic entertainment during the cold winter months. Today teams from 17 nations, from Argentina to the Philippines, compete in a biannual world tournament. Underwater cameras stream the matches over the internet.

Rive fell in love with the sport’s complexity. Because you can make plays from above or below another player, it’s fully three-dimensional. And then there is the matter of holding your breath. Underwater hockey tests your limits as a land mammal. It pits you against the voice inside your brain begging you to come up for air. “You learn to do amazing things by holding your breath when your body’s telling you that you need to breathe,” Rive explains later. “You’re having this debate,” he says, and then he dramatizes it: “I have to score.” “But you need to breathe.” “No, no. I want to score.” “OK, I’m giving you a warning. I’m going to turn the lights off.” “No, keep the lights on just a little longer.” “I’m going to turn the lights off.” “No, no. I need to score.”

In these situations, a heated contest for the puck in front of the goal can stop, suddenly and noiselessly, as one competitor quits in the name of oxygen, leaving an open target. “You learn how to push yourself under all conditions,” Rive says. “You’ve just got to push yourself further than the next person.”

What’s true in the pool also holds in the boardroom. The solar-power industry may well be on its way to that asphyxiation point. SolarCity’s biggest rival, SunEdison, filed for Chapter 11 in April. Meanwhile, SolarCity has more than $3 billion in debt on its balance sheet. Analysts have openly wondered how much longer the company will be able to pay its bills — even after Tesla’s buyout.

The Rives and Musks prefer to think through this fear rationally. “We’re super-logical,” says Peter Rive. “If I try and I fail, that’s not so bad. If I succeed, holy shit. But if nothing is done, it’s worse than having tried and failed. You think through the iterations of action and nonaction and compare all the worst-case outcomes.” As they see it, doing the thing everyone else thinks is crazy is the only rational way to behave. And anyway, adds Peter, how bad is it really? “Think about the truly hard problems that Elon is working on,” he says.

In the eyes of the Rive brothers, and everyone at SolarCity, Elon Musk is the smartest, most capable. The best. His strategic vision is honored above practically anything else, including available information. Rive has compared his cousin to Neo in The Matrix — “He can see the zeros and the ones,” Rive told EE News, adding that he believes Musk steers the company away from “the invisible walls,” or obstacles that only his cousin can foresee. “He may be wrong 100 times,” Rive told me. “But I’ll be wrong 500 times.”

The result is that Rive and SolarCity put their faith in Musk’s vision even as others slam those plans as ill-advised or reckless. It was Musk’s idea for SolarCity to build a massive $850 million solar panel factory in Buffalo, New York, a move that plunged the company into a completely unfamiliar business. It was Musk who urged the company to expand as fast as it did and to develop exotic financial products to provide the fuel. Those outside the Rive-Musk bubble look on with a combination of shock and awe. “I think Elon Musk is a genius, and I don’t use that word lightly,” Charlie Munger, the vice-chairman of Berkshire Hathaway, told a conference audience in 2014. “He’s also one of the boldest men to ever come down the pike.”

Indeed, it is Musk who ends up garnering all the SolarCity headlines, even though he’s not a co-founder of the company and Rive is the company’s CEO. “Why You Might Buy Electricity From Elon Musk Some Day” was the title of an article in The Atlantic, which did not once mention Lyndon Rive’s name. “Lyndon is a very thoughtful person,” says Ben Kallo, a senior analyst at Robert W. Baird & Co., who covers the alternative-energy industry. “But Elon Musk overshadows anyone who works for him.”

Rive says he has no problem with that. “Elon is one of the greatest people in the world,” he told me. “His vision and commitment to helping humanity is off the charts. I’m fortunate to help him.”

In the time since I met Rive, the going has gotten even tougher for SolarCity. At the end of August, the company announced plans to lay off 108 employees from its offices in San Francisco and San Mateo. The Rive brothers announced they planned to cut their own salaries to $1 a year. In the past three months, the company had lost $55 million, less than in previous quarters but a long, long way from turning a profit. The company now has $3.25 billion in debt.

Rather than give up, SolarCity is doubling down — not unlike the way Musk refused to back down at Tesla. In a filing in August, the company announced that its latest bond fund would seek money from consumers, not just banks. To get things going, Musk pledged $65 million of his own money to the $124 million fund. Peter and Lyndon Rive each pledged $17.5 million.

Yet critics continue to pounce. They point out that the company, which installs fewer and fewer solar-energy systems each quarter, will need to break all records in the fourth quarter to meet even the low end of its 2016 goal. And critics have continued to criticize the Tesla acquisition as a bailout of a failing company. “The insiders are perpetrating a cruel joke on the non-insider Tesla shareholders,” wrote a financial blogger on seekingalpha.com, in a post titled “Musk Fiddles as SolarCity Burns” (yet another dispatch that makes no mention of Rive). “Tesla will be overpaying for SolarCity even if the latter were to be given away for free.”

Rive seldom loses his cool, but you can hear the agitation and impatience in his voice when responding to his critics. “I’m not angry — that’s the wrong emotion,” he says. “But people don’t understand the financials of SolarCity.”

Besides, Rive and Musk’s ambitions are so much bigger than mere survival. They still plan to open the massive panel factory in Buffalo, maybe not as early as originally planned, but soon. And instead of just solar panels, they now propose to build entire solar rooftops paired with Tesla-built batteries. “All the naysayers will realize that in four to five years, we’ll no longer build power plants the way we do today,” Rive says. Rather, municipalities will be able to tap the energy gathered on rooftops and stored in all those batteries. Excited now, he goes full wonk, speaking in nearly impenetrable technical terms. As I struggle to keep up, I suddenly recall that this is a guy who barely graduated high school — he’s a total autodidact.

SolarCity will struggle, of course. Investors will continue to doubt them. Critics will continue to harangue Musk and dismiss Rive. But Rive believes there’s still plenty of oxygen left before the lights get turned out. He’s only just started holding his breath.

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