The number of photovoltaic building permits issued for Oahu fell nearly 50 percent in October compared with the same month last year.

The City and County of Honolulu issued 367 PV permits last month, down 49 percent from 720 in October 2015, according to data released Monday by Marco Mangelsdorf, who tracks rooftop solar permits and is president of Hilo-based ProVision Solar.

Year-to-date permits were down 29 percent from the same period last year. The city issued 4,156 permits from January to October compared with 5,852 in the year-earlier period.

Permits have been generally in decline since the state ended a popular solar energy incentive program last fall. The solar industry has been struggling as a result.

In October 2015 the state Public Utilities Commission terminated a rooftop incentive program that credited customers the retail rate for the excess energy their systems sent to the grid.

When NEM ended, the PUC replaced it with two other options, called grid-supply and self-supply. And now only one of the two incentive programs, self-supply, is available.

All of Hawaiian Electric Co.’s service territories have reached the state’s grid-supply limit. The program lets customers export excess energy to the grid and credits owners 15 cents a kilowatt-hour for the extra energy their systems send. The rate is roughly 8 cents less than the retail rate that had been offered through the NEM program.

Those in the self-supply program cannot send excess energy into the grid, but can draw energy from the grid. Most systems need batteries to meet self-supply requirements.

Last week HECO and its sister companies — Maui Electric Co. and Hawaii Electric Light Co. on Hawaii island — announced that the number of applications they had received for the self-supply program had surged from 50 at the beginning of October to 234 at the start of November.

Despite the self-supply program gaining interest, the recent numbers still aren’t enough to turn around the solar industry’s decline, Mangelsdorf said.

“Even with a considerable acceleration of (self-supply) sales, there’s no way this kind of volume can sustain the state’s once-shining solar electric industry,” he said.

Some 442 solar employees have lost their jobs since the PUC ended the solar incentive program in October 2015, equaling a 42 percent reduction in the solar workforce over the last year.

Last month PUC officials said they would be starting a process in which they may reconsider the rules for grid-supply and self-supply.