Federal grid watchdogs are raising alarm bells over a solar panel design flaw that could result in power outages nationwide if not addressed, based on the results of a near year-long investigation into a major outage last summer in California.

The North American Electric Reliability Corporation on Thursday issued the results of the investigation on an August 16, 2016, outage that occurred in southern California as a result of a wildfire that caused a large chunk of solar rooftops to trip and stop delivering electricity at a critical time.

"With the proliferation of solar development in all interconnections across North America, the results of this disturbance analysis needs to be widely communicated to the industry highlighting the present potential for widespread solar resource loss during transmission faults" on the electric grid, the report stated.

The results of the investigation were released at the same time the solar industry touted new quarterly gains in a market report issued Thursday. "Solar is delivering more clean energy, adding jobs 17 times faster than the U.S. economy and creating tens of billions of dollars in investment," said Abigail Ross Hopper, president and CEO of the Solar Energy Industries Association.

NERC, which was sanctioned by Congress in the 2005 energy law to help regulate the power grid against blackouts, issued a special advisory called a "NERC alert" to the solar industry, advising it that the issue must be taken seriously. The agency's alert, "along with further study and outreach, will assist the industry in taking steps to resolve this issue and ensure interconnection reliability," the report stated.

NERC was assisted in its investigation by the nation's top grid watchdog, the Federal Energy Regulatory Commission. FERC had been concerned about blackouts over the last year due to California's increased dependence on solar rooftop electricity, which is part of its plan to hit climate and clean energy targets.

FERC had been concerned that southern California could run out of natural gas after a massive leak at an underground supply facility north of Los Angeles shut down the facility. But the problem stems from the natural gas supply being used to power a fleet of fossil fuel power plants that are meant to back up the grid as solar ramps up in the morning and ramps down in the evening.

Thursday's investigation adds a new wrinkle to the complexities of managing the grid stemming from solar power arrays themselves. The solar panels did not shut down, per se, but the inverter boxes that regulate the movement of electricity from rooftops to the broader grid malfunctioned. The inverter boxes tripped, or turned off, after the wildfire raged around Southern California Edison's interstate transmission lines, which caused problems in electricity delivery due to fluctuations in output on the lines. When the solar panel inverters in the region were tripped, it resulted in the loss of 1,200 megawatts of electricity, enough to supply power to more than 1 million homes.

The report said the solar energy industry and utilities are working with the manufacturers of the inverters to make modifications that would stop such a broad shutdown of the power supply.

NERC concluded that solar inverters are "susceptible to erroneous tripping" and recommends that manufacturers of the inverter boxes deal with the problem, which it added that they are.

"Manufacturers that experienced this type of tripping during the Blue Cut fire event have recommended changes to their inverter settings to avoid this erroneous tripping," the report said. "This change will add a time delay to inverter frequency tripping that will allow the inverter to 'ride through' the transient/distorted waveform period without tripping.

"Solar development owners and operators involved in this event are working with their inverter manufacturers, California Independent System Operator (CAISO), and SCE to develop a corrective action plan for implementation of changes to inverter parameters," it added.