The number of photovoltaic permits issued in Honolulu County more than doubled in September, according to data compiled by Marco Mangelsdorf, who tracks rooftop solar permits and is president of Hilo-based Pro Vision Solar.

The 458 permits issued were the most in any month in more than three years and were up 162% from 175 in September 2018. Over the first nine months of this year, the Honolulu Department of Planning and Permitting issued 2,482 PV permits, up 26% from 1,963 in the year-earlier period.

Of the top four solar companies on Oahu, No. 1 RevoluSun is up 74% in its permits; Hawaii Energy Connection, 72%; Alternate Energy, 76%; and Sunrun, the state’s former industry leader, is down 64%.

On the Big Island the County of Hawaii issued 101 PV permits last month compared with 67 in September 2018, an increase of 51%. In Maui County 563 PV permits were issued compared with 418 in 2018, for an increase of 35%. And on Kauai 365 PV permits were issued compared with 214 last year, a jump of 70%.

Over the first nine months this year across Hawaii’s four counties, there were 4,047 solar electric permits issued compared with 3,387, an overall increase in the state of 19%.

“Interestingly, while Hawaii … enjoys the nation’s highest penetration rate of residential solar (and) has experienced a notable increase this year, California, which has more PV deployed than the rest of the country combined, is down by 18%,” Mangelsdorf said.

”One reason for the difference is likely the adoption of energy storage. Somewhere over 70% of all PV systems permitted in Hawaii this year include batteries. In California that number is still in the single digits. That said, with the debacle of PG&E days-long power outages across much of the state recently, the interest in including Tesla Powerwalls and LG Chem products, the dominating players in residential storage, and other battery platforms will likely spike as it never has before.”