Solar installations across Hawaiian Electric Cos.’ service territories rose in 2017 by the most megawatts in five years even as the number of permits that were issued continued a multiyear downward trend.

The state’s dominant utility said 109 megawatts of solar were installed in 2017 to bring the cumulative total for Hawaiian Electric Co., Maui Electric Co. and Hawaii Electric Light Co. to 695 megawatts, up 19 percent from 586 megawatts in 2016, according to data released Thursday. Solar installations have grown every year since 2005 as the state gets closer to its goal of achieving 100 percent clean energy by 2045.

The increase in solar installations and the decrease in photovoltaic rooftop permits likely reflect the lag time between pulling a permit and the actual solar system build-out, according to HECO spokeswoman Shannon Tangonan.

“It could be that permits were pulled in 2016 or earlier and the system didn’t get built until 2017,” Tangonan said. “Sometimes the build-out never takes place.”

Solar permits that were issued fell 28 percent last year in Hawaii County, 35 percent in Honolulu County and 59 percent in Maui County, according to data pulled by Marco Mangelsdorf, who tracks rooftop solar permits and is president of Hilo-based ProVision Solar. In Kauai County, which falls under the Kauai Island Utility Cooperative, permits fell 12 percent, according to Mangelsdorf.

“One inescapable reality is that sooner or later the actual installations do catch up with the lower permit numbers,” he said.

Hawaiian Electric Cos. said the amount of solar installations last year included 82,000 private rooftop solar systems connected or approved. It also includes the 27.6-megawatt Waianae solar facility, which provides some of the state’s lowest-priced renewable energy.

Private rooftop solar installations and approvals as a percentage of total customers rose in 2017. About 20 percent of HECO and MECO residential customers had rooftop solar installed or approved for installation. That was up from 19 percent for both companies in 2016. The number of HELCO residential customers to have solar installed or approved was 16 percent in 2017, matching the percentage the year before.

“We ended 2017 with the largest year-to-year increase of installed solar since 2013, and we anticipate even higher numbers by the end of this year,” said Jim Alberts, Hawaiian Electric senior vice president of customer service. “We’re excited about new solar programs on the horizon … and new grid-scale projects underway on Oahu and Maui.”

Hawaiian Electric Cos. said 135 megawatts produced by six separate projects will come online this year on either Maui or Oahu, including HECO’s 20-megawatt solar facility at Joint Base Pearl Harbor-Hickam. That project will produce the lowest-­priced grid-scale solar in the state.