Hillary Clinton's pledge that she would boost solar power sevenfold by 2020 isn't as far-fetched as it sounds, but it would take everything going perfectly to meet that mark.
While the goal to boost U.S. solar capacity to 140 gigawatts, up from 20 gigawatts today, is "aggressive," experts said, it's still doable given recent growth trends and falling technology prices.
"Although it's a big number ... it's not a number that I'd characterize as entirely unreasonable. You would not have been able to say that even four years ago. That fact alone really demonstrates the tremendous progress the solar industry has made," Francis O'Sullivan, director of research and analysis with the MIT Energy Initiative, told the Washington Examiner. "It shines a light on how solar is no longer this niche business."
A calculation by the Examiner showed that achieving the 140 gigawatt goal is possible, assuming recent growth trends hold constant. Using Solar Energy Industries Association data on installed solar capacity and projections for 2015 and 2016, the Examiner used a 37 percent annual growth rate — a middle ground in the data — to chart out new additions through 2020. That analysis showed the U.S. would install about 151 gigawatts of solar capacity at the end of 2020.
Still, the Democratic presidential candidate's projections dwarf projections from mainstream analysts such as Bloomberg New Energy Finance, Greentech Media and the U.S. Energy Information Administration. Even more ambitious estimates fall short of Clinton's goal. UBS, for example, expects just shy of 100 gigawatts of solar but in 2025, five years after Clinton's mark of 140.
One of the major questions about the feasibility of Clinton's plan is whether the 30 percent investment tax credit for solar systems is renewed.
The credit is scheduled to end after 2016. It is a key driver of solar's growth as third-party installers of rooftop solar rely on being able to collect that incentive. Without it, industry group Solar Energy Industries Association predicts new installations would decline 57 percent in 2017 compared with anticipated 2016 figures.
The long-term uncertainty of the tax credit might plague new construction in 2017 and 2018, as investors might cool to the idea of undertaking projects, Elias Hinckley, who heads the energy practice at Sullivan and Worcester LLP, said in an email.
Still, that downturn may be short-lived. Recent price drops are expected to make solar more competitive with or without subsidies, as will reduced "soft costs" such as siting fees, Hinckley said.
And the cost of using natural gas and coal in electricity is expected to increase as new regulations, such as carbon emissions limits on power plants, take root, added Chris Nelder, an energy analyst.
"You then have to balance the outlook for the [investment tax credit] against how necessary it will actually be circa 2020, by which time many analysts ([especially] at the big banks) believe that solar will be the cheapest new capacity around," Nelder said in an email.
Much of the recent solar boom is a result of falling prices. The Obama administration has said solar panel costs dropped 76 percent from 2009 through 2013. But that steep of a discount isn't expected to continue in the next couple of years, though prices likely will still fall, said Dan Bakal, director of the electric power program at the business sustainability group Ceres.
"Because it's come down so much it's actually quite competitive now in so many parts of the country. However, most analysts are not predicting it will come down as quickly as it has in the last five, six years," Bakal told the Examiner.
On top of that, total installed electric capacity is 1,060 gigawatts, according to the EIA, and demand is expected to remain flat for at least a decade. Pushes for energy efficiency could further restrain demand, while natural gas facilities currently only run about 50 percent of the time and have room to provide more power if needed, said Constantine Samaras, an assistant professor of civil and environmental engineering at Carnegie Mellon University.
"So without a focused climate policy there might not be a giant demand for new power plants other than mainly displacing those that are retiring," he said in an email, adding that Clinton's plan was "ambitious and doable."
Clinton's campaign suggested that the carbon emissions rule will bring the share of the electricity mix for all renewables to 25 percent, up from 16 percent. Her team wants renewable energy to comprise one-third of the electricity system by 2027.
But solar's rapid growth has occurred largely in hotspots such as the Southwest that can't be relied on to carry future additions at the same rate, noted O'Sullivan. For rooftop solar, saturation in some markets could be a deterrent to new projects. That's because third-party financing depend on a high spread between peak power prices — when it's sunniest — and system costs. As solar expands, the return on investment for each solar panel decreases.
"That development, those dynamics, effectively undermine solar's competitiveness. And in those instances solar costs have to fall faster than the prices that investors are receiving," O'Sullivan said.
Instead, then, the growth in solar will have to come from untapped markets in the coming years, O'Sullivan said. Incentives likely will be needed to encourage that kind of activity, he said.
Utilities, though, remain a potential bright spot, said O'Sullivan and Bakal. They are increasingly taking the lead on big solar projects and likely will continue to do so as state renewable electricity mandates ramp up and federal regulations kick into gear.
According to the Solar Energy Industries Association, utility-scale solar grew by 4 gigawatts in 2014, a 38 percent increase over the previous year to represent the largest growing solar sector. It's "still early days" for utility investment in solar, Bakal said, as many are still trying to figure out what role their state regulators will allow them to play in owning or distributing solar power to customers.
"I just see the pace of change happening for solar the way that change happens in high tech. This is not your traditional electric power technology that requires just so much engineering and siting issues and safety and just all of that stuff that bog down so many of the traditional electric power generation sources. Solar is just so scalable," Bakal said.