Workers install solar panels on a rooftop on February 20, 2015, at a home in Palmetto Bay, Florida. KERRY SHERIDAN/AFP/Getty Images

In recent years, the growth of the rooftop solar market has been astounding. According to the Solar Energy Industries Association, the growth rate for at-home solar has been above 50 percent for three years running (2012, 2013, and 2014).

But if a new study is to be believed, the changes have only begun.

The way we get power is “at a metaphorical fork in the road,” says the new report released today by the Rocky Mountain Institute, an influential energy policy think tank. The reason is not just rooftop solar but, beyond that, the growing feasibility of home electricity systems combining solar panels with batteries for storage of energy.

“Grid-connected self-consuming solar will become economic for nearly all customers imminently, with grid-connected solar plus-battery systems following soon after,” notes the study, which was co-authored by Homer Energy.

Customers will chose these options, the study finds, because they’ll save money on their bills. And once they can not only generate their own power from the sun, but can also store it until they need it (including overnight, when there’s no sun shining), the old model of buying all your power from a single utility company could be strongly challenged.

The new report agrees with another recent study, just out in the journal Energy Policy, that people will not be abandoning the grid en masse. But over time, more and more of the electrons that they use to power their homes and lives could. While most people will stay connected so that they’ll always have backup power, they’ll increasingly generate and store more and more of their own, and potentially sell it back to the grid (a key reason to remain connected).

The Rocky Mountain Institute study looked at five different U.S. cities in very different regions — Louisville, San Antonio, Los Angeles, Honolulu and Westchester, N.Y. — and modeled how soon it would make economic sense for people in each place to shift first to rooftop solar (or PV) and, second, to rooftop solar with battery storage.

The upshot is that — at least based on the models used in the study — the revolution starts surprisingly soon in many places:


Rocky Mountain Institute, “The Economics of Load Defection,” April 2015.

“New customers will find solar-plus-battery systems configurations most economic in three of our geographies within the next 10-15 years,” says the study. In Westchester County, it projects, the traditional grid could provide just 25 percent of people’s power by 2030. Granted, as you can see, the change could take longer to materialize in other regions.

The research aligns well with the views of NRG Energy CEO David Crane, who recently remarked that “the distributed future will be utterly destructive of the utility model that we now have. No one wants to spend more on electricity than they have to.”

But the Rocky Mountain Institute study suggests that if utilities can’t beat them, they can still join them. It describes the possibility of an “integrated grid” in which lower carbon emissions and more customer choice have economic benefits that strengthen the system as a whole. Meanwhile, utilities could get in the business of helping consumers finance these new home electricity systems, or could even own some of their components.

Whatever happens, the report notes, the business and policy moves made today will be pivotal. “Decisions made in the short-term can set markets down extremely different paths,” the study concludes.