Maui Electric Co. said Wednesday that the county has hit the limit of rooftop solar systems that can send power to its grid.

After this week, the Maui utility will not approve any new rooftop solar systems on Maui, Lanai or Molokai that send power to the grid. Under the previous policy, MECO customers could send excess solar power to the grid and receive a credit, which often would reduce their monthly electric bill to less than $20.

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.”

Jim Alberts, senior vice president of customer service at Hawaiian Electric Co., said self-supply is a good option for customers and the utility is open to looking into other programs for solar customers.

A coalition of groups in the solar industry said self-supply isn’t a good replacement, in part because batteries are too expensive.

“The utilities pretend that customers can instead choose the self-supply option, but the utilities’ own reports show that self-supply is not yet a viable replacement,” said Hajime Alabanza of the Hawaii Solar Energy Association in a statement. “It’s disingenuous for the Hawaiian Electric utilities to claim self-supply is a real customer option when they have refused to interconnect a single self-supply system in Hawaii.”

Robert Harris of the Alliance for Solar Choice said, “We’ll never get to 100 percent renewable power in Hawaii if monopoly utilities are allowed to block consumer access to solar energy.”

Hawaii has set a goal of generating 100 percent of its electric power from renewable sources by 2045.

In October, the state Public Utilities Commission ended a popular incentive program that offered owners of solar-energy systems a credit equal to the retail rate for the excess energy that their systems sent into the grid. The PUC replaced it with two programs.

Only one of the two programs, called grid-supply, allowed customers to continue exporting excess energy into the grid.

Grid-supply credits new solar owners 15 cents a kilowatt-hour for the extra energy their solar systems send into the grid, roughly 8 cents less than the retail rate that had been offered through the original program. The PUC put a 35-megawatt limit on the total amount of energy generated from the grid-supply program statewide. Maui County’s limit was 5 megawatts.

MECO said that approved systems and applications filled the 5-megawatt capacity limit for Maui, Lanai and Molokai this week.

The state is set to revisit the solar rule change in October 2017.

“In the meantime, we believe the self-supply option is a good alternative,” Alberts said. “We’re completely open to work with all the parties about what the next phase looks like and what the new programs look like.”

The solar alliance wants grid-supply to be expanded soon.

“It’s our hope that the PUC will act quickly to raise the grid-supply cap on Maui and throughout the state of Hawaii,” Harris said.

“Battery storage is going to revolutionize everything, but it is a shame that the state has put a cap on the amount of solar that Maui residents can produce when most people agree there is room for more solar on the grid,” said Stuart Coleman of Surfrider Foundation, Oahu Chapter.