The number of rooftop solar permits issued for Oahu dropped 40 percent in November compared with the same month last year.

The City and County of Honolulu issued 434 PV permits last month, down 40 percent from 726 in November 2015, according to data released Tuesday by Marco Mangelsdorf, who tracks rooftop solar permits and is president of Hilo-based ProVision Solar.

Year-to-date permits were down 30 percent from the same period last year. The city issued 4,590 permits from January to November compared with 6,578 in the year-earlier period.

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

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, called Net Energy Metering.

When NEM ended, the PUC replaced it with two other options, called grid-supply and self-supply. Now only self-supply is available.

Self-supply prohibits solar owners from sending excess energy into HECO’s grid. Most systems need batteries to meet self-supply requirements.

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.

There are 255 self-supply applications submitted to HECO. On Oahu 195 of them have been approved by the utility for installation. Two have been installed and turned on.

Potentially opening up the grid-supply program again, the PUC also issued an order earlier this month allowing those who did not follow through with their NEM systems — 5,055 on Oahu — to withdraw and be replaced by new customers interested in grid-supply.

“For those of us in the local PV industry, the hope is that the elimination of the (NEM) deadwood over the months to come will lead to the approval of a burst of (grid-supply) applications, which have been languishing since the (grid-supply) caps were reached earlier this year,” Mangelsdorf said.