Solar applicants on Maui are pushing the limit, while Oahu and Big Island are well past the halfway point for the capacity for residential solar systems that can export excess power to the grid and receive credit.

The number of solar systems plus applications waiting for approval in Maui County has hit 103 percent of the cap state regulators placed on rooftop solar in October.

Oahu is nearly 60 percent full, and the Big Island is at 54 percent.

The Public Utilities Commission replaced a popular solar incentive, known as net energy metering, with a new “grid supply” system last fall and put a 35-megawatt cap on the new program. The grid-supply program credits solar energy customers about 8 cents less per kilowatt-hour than the full retail rate paid under net energy metering.

The cap breaks down to 25 megawatts on Oahu and 5 megawatts each for Maui County (which includes Molokai and Lanai) and the Big Island. Oahu has reached roughly 59 percent of the 25 megawatt cap.

Maui Electric Co. said in June it stopped approving the solar systems because the county hit the 5-megawatt cap regulators placed on the program.

“They reached their cap, but clearly that hasn’t stopped people from submitting their packages to them,” said Marco Mangelsdorf, president of Hilo-based ProVision Solar.

Maui County residents who want to install new solar systems will now have to buy batteries to hold any excess power generated by the panels. They can still draw power from the grid when needed but can’t send power to the grid. The solar-plus-battery systems are called “self-supply.”

In May a coalition of solar energy groups asked state regulators to increase the limit on excess power that photovoltaic systems are allowed to send to the grid.

The Hawaii PV Coalition, the Hawaii Solar Energy Association, Sunpower Corp. and the Alliance for Solar Choice said they will likely fill any remaining capacity on all islands by the beginning of August.