Dispatching clean-cut kids to peddle expensive solar panel systems door to door—it may sound like a concept for a Simpsons episode, or for a 21st century update of The Music Man.

But it has proved to be a path to riches for at least one American firm. In 2011, Vivint, an alarm company based in Utah, decided to get into the solar business. It deployed a mobile sales force, attracted a big investment from the private equity giant Blackstone Group in 2012, and quickly built its subsidiary, Vivint Solar, into the second-largest panel installer in the country, behind Elon Musk’s SolarCity. Last Wednesday, it staged an initial public offering that raised $330 million and valued Vivint Solar at $1.3 billion.

Vivint’s rapid success—it has convinced nearly 22,000 homeowners to go solar—highlights a recurring theme. When it comes to energy, resources matter, such as having lots of natural gas or animal manure. And technological breakthroughs matter, too, like substituting aluminum for steel in pick-up trucks. But what’s really helping America catch up to the rest of the world in renewable energy and reducing emissions is innovation in business models, marketing, finance, and selling. The greatest advances happen when good, old-fashioned, earnest American hucksterism meets the massive consuming force of the American people.

Solar power has grown rapidly in the U.S. in recent years, partly because the cost of panels has come down significantly and partly because of new methods of piecing together and selling those panels. On the wholesale level, we’ve seen the construction of giant solar farms in the southwest, some with the capacity of up to 250 megawatts or more—the first of their kind built in the world. At first constructed only with government backing, these solar farms are now attracting private capital.

On a retail level—selling systems to homes—the innovation has come in the marketing and sales of the systems. For years, the high upfront cost of solar systems acted as a barrier to adoption. In response, SolarCity pioneered the solar lease. With leases, homeowners don’t own the panels, but they do get to use the electricity produced by them without putting much money down. Vivint Solar relies on a simpler model: a power purchase agreement. Under a PPA, Vivint Solar owns the panels, while homeowners put no money down and agree to buy the output of the panels for 20 years, generally at a fixed price that is 15 to 30 percent below what they are currently paying. In states where regulations permit so-called “net-metering,” the homeowner gets the credit when the panels produce more than the house uses. That’s part of the reason Vivint Solar operates only in states where net metering is allowed and where the combination of solar resources and high utility prices make a PPA appealing. (Vivint Solar is active in seven states: Arizona, California, Hawaii, Maryland, Massachusetts, New Jersey, and New York.)

Created in 2011, Vivint Solar was spun out of Vivint, a 15-year-old company based in Provo, Utah, with a distinct business model. Each summer, Vivint dispatches a few thousand college students, mostly from universities in Utah, to sell alarm systems door to door, on commission, in every state; the Vivint Solar subsidiary taps into the same labor force. Many of the salespeople already have experience as Mormon missionaries—about one-half of Vivint Solar’s sales force is Mormon—so they’re comfortable peddling new ideas to complete strangers and dealing with rejection. (A Reuters reporter who embedded with Vivint salespeople captured the strange phenomenon of door-to-door power plant sales.)

Another wrinkle in Vivint Solar’s business model: It directly employs the people who design, install, and maintain the systems. Marrying one-stop service to a simple power purchase agreement “takes all the complexity out of solar,” says Greg Butterfield, chief executive officer of Vivint Solar. This is a retail business that depends heavily on personal salesmanship and an ability to convince people to purchase a complex service. The big idea is not simply to recruit converts to solar, but for the converts to then function as evangelists. Butterfield says that salespeople typically return to a home on the day a system goes live. Why? “All the neighbors come around and talk,” he says. Later, when the first bill arrives—and the customer can see the savings for the first time—the salesperson returns again and asks for referrals.

This model works, but it takes a lot of effort and cash, with heavily front-loaded costs. Vivint Solar has to hire and train its workers, build offices, and install the systems before it starts collecting monthly payments. It’s shown impressive growth so far, especially considering that the company hasn’t relied on acquisitions—as data in the company’s prospectus shows, the company sold 2,669 systems in 2012, 10,521 systems in 2013, and another 8,625 in the first half of 2014. All told, the company has placed panels on about 21,900 houses in less than four years, with a collective capacity of 129.7 megawatts.

Vivint’s methods may be a pretty labor-intensive way of building the equivalent of a small power plant. But the company’s innovation—and value—lies precisely in the way it is turning electricity production into a door-to-door sales business.