Prices for panels are down more than 65 percent in five years, to less than 70¢ a watt. What’s next? 

One word, Ben: financing.

Building a solar generating facility—either a massive one in a desert or a tiny one on the roof—involves serious up-front costs. In extreme cases, the cost of capital can make power almost 50 percent more expensive than it would otherwise be, says a report released Tuesday, Feb. 24, by the independent German research group Agora Energiewende. These costs can even influence the ultimate price of electricity more than the amount of sunlight a region receives.

But the industry is growing up in ways that are leading to both lower costs overall and, as GreenTech Media has reported, faster installations. Solar developers, banks, nonprofits, and other industry players are creating tools that are standard in mature financial markets. These are the business practices that don’t make for dramatic headlines but need attention if the industry is going to reach adulthood: credit ratings, due diligence standards, and in general, cheaper ways to find and close deals. The easier these things become, and the more deals are done, the less risk investors face.

It’s gradual, but gradual like a locomotive.

“Most scenarios fundamentally underestimate the role of solar power in future energy systems,” says the Agora report, which focuses on larger systems. In many cases, it says, “this can easily be explained by the use of outdated cost estimates for solar photovoltaics.” 

So when do these things start showing up around the neighborhood?

The U.S. solar market continues to grow at a gallop in many parts of the country. California is responsible for about half of the total installations, with huge opportunities on the horizon in Texas. Arizona, Hawaii, New Jersey, New York, and the Carolinas have all seen solar boomlets.

To see why, watch the yellow bars shrink from left to right: 

The chart shows two key trends in past and projected costs of U.S. solar installations. The yellow is the cost of silicon, which continues to decline toward 30¢ to 35¢ a watt by 2020, according to Bloomberg New Energy Finance. The Agora report is even more bullish. “An end to cost reduction for power from solar photovoltaics is not in sight,” the analysts write. That holds even if solar systems see no more technological improvements, a conservative and unlikely assumption.

Critically, the red bars in the chart show a similar decline, mostly in “soft costs,” a grab-bag term that can include the many impediments to closing deals, such as high marketing, sales, and development costs or the expense of hiring lawyers to research and design every deal. These costs should shrink as the solar industry abandons ad hoc practices and makes itself more attractive to large investors with enormous sums of money.

“That’s now the hard work being done,” said Jeff Weiss, co-chairman and managing director of BeEdison, which has developed software that helps investors standardize the diligence and risk-assessment work that goes into every deal. “If that gets done, that will unleash tens of billions of dollars for investments.”

The chart is based on data included in a January Bloomberg New Energy Finance report on the North American market. The totals represent an average of data on residential solar markets in all 50 states, including all the laggards.  

And when do they show up on my roof?

You don’t have solar?

Kidding. As much as Americans might want to tell off their power utilities and cut the wire forever, we’re not there yet, even in states that are ahead of the game. A few things still keep us tethered to the grid.

First, and most famously, the sun doesn’t shine all the time. So unless you have enormous batteries to run the house on, which no one does (yet), phone charging and refrigeration would serve at the pleasure of cloud cover and time of day. 

Second, state subsidies that pay residential solar generators for power they send back to the grid are another thing helping keep prices down in several regions. Why cut off from the grid when you can reduce your bill, or even make money, by selling the power you produce but don’t use? 

Finally, grid backup isn’t such a bad idea as insurance. If your inverter blows, it’d be nice to have a fallback until the new one arrives. 

Remember Solyndra?

The antihero of renewable energy in the 2012 presidential election was Solyndra, the solar startup that failed spectacularly by defaulting on $535 million in loans backed by the U.S. (The same Department of Energy loan guarantee program would go on to make money, through interest.)

Earlier this month, SolarCity, the residential solar company founded by Elon Musk, leased Solyndra’s old factory. It’s the perfect symbol for solar’s transition from federally supported, promising technology to a self-sustaining industry. 

Good timing, too. This chart shows the projected U.S. solar buildup through 2017, when federal tax credits will drop from 30 percent of investment in a project to 10 percent.  

Large-scale, utility-type deals, in red, are expected to take a big hit right away, which is why developers have pushed all the deals they can into this year and 2016. Note that residential and commercial projects, in yellow and purple, are expected to stay about the same in 2017, despite the cut in U.S. subsidies. There’s a case to be made that the subsidy cut will actually encourage solar deals, because qualifying for the tax credits puts onerous, often expensive requirements on the parties involved. 

That doesn’t mean the pressure to make the economics work is off.

It does mean than in a few years, technology long confined to environmentalists’ fantasies has become a viable source of power for many places under the sun.