Oahu is half full.

Maui County is 70 percent full, and the Big Island is 38 percent.

That’s how close each county is to reaching its capacity for residential solar systems that can export excess power to the grid and receive credit.

State regulators placed the limit on rooftop solar in October, and Hawaiian Electric Co. released its latest numbers Tuesday.

The Public Utilities Commission replaced the popular net energy metering solar incentive 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. Net energy metering paid the full retail rate.

The PUC said it placed the limit on new PV systems to make room on the grid for other sources of renewable energy.

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 52 percent of the 25 megawatt cap. There are 1,547 grid-supply systems on Oahu currently waiting approval or approved for installation.

The grid-supply applications that have passed Maui Electric Co.’s first review equal roughly 70 percent of the 5-megawatt cap regulators placed on the program.

The applications that have passed Hawaii Electric Light Co.’s initial review equal roughly 38 percent of the 5-megawatt cap regulators placed on the program for the island.

Last month 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.

On May 25 HECO opposed the request to increase the cap, saying the commission didn’t put a limit on the program for the solar industry to use it as a sales tool.