Oahu residents looking to get rooftop solar energy systems soon won’t be able to send their excess energy into the grid.

Hawaiian Electric Co. said Wednesday that Oahu has nearly reached the capacity that the state Public Utilities Commission put on solar systems that export energy to the power grid. As of Friday, approved systems under the grid-supply program totaled nearly 23 megawatts.

The PUC put limits on the total amount of energy it would accept from solar systems that send excess energy to the grid when it ended a solar incentive program in October called net energy metering. NEM credits customers the full retail rate for the energy they send to the grid. Many solar energy system owners lowered their electrical bill to approximately $17 a month through the program.

After ending that program, the PUC left customers with two options: a solar system with a lower credit for excess energy sent to the grid; or a solar system, no credit and a battery.

The first program, called the grid-supply program, credits customers roughly 15 cents a kilowatt-hour, which is approximately 10 cents lower than NEM. Grid-supply also had a set amount of systems it could accept. Oahu’s limit is 25 megawatts, Hawaii island’s limit is 5 megawatts and Maui County’s limit is 5 megawatts. Maui and Hawaii island have reached the limit.

The other program, called self-supply, is what is left for customers. Self-supply prohibits solar owners from sending excess energy into HECO’s grid. Most systems need batteries to abide by self-supply requirements.

Both HECO and the members of the solar industry said that the self-supply program can be a good option for customers.

HECO said that solar still remains a viable option for customers who want it.

“This is the next evolution in solar energy systems,” said Jim Alberts, Hawaiian Electric senior vice president for customer service. “Solar power is a significant part of our plans to reach 100 percent renewable energy and an important option for our customers and we expect more customers will install self-supply systems.”

HECO said there are two self-supply systems on Oahu that have been installed and turned on, with 20 more approved for installation.

San Francisco-based Sunrun Inc. installed the first self-supply system on Oahu in May.

The system included two Tesla Motors Powerwall batteries linked to a solar system.

The company said the typical system with two Powerwalls and 28 panels would cost homeowners $40,000 without tax incentives and roughly $20,000 after the credits. Homeowners can lease the system with no down payment and pay Sunrun 19 cents a kilowatt-hour for 20 years.

Solar industry leaders said it is important to create an incentive program for batteries because grid-supply might run out before self-supply takes off.

The solar industry hasn’t been faring well after the end of NEM as building permits for the solar energy system have declined steadily for the past year. The decline largely has been attributed to the state ending the popular NEM program.

“The decision to end the NEM program and replace it … has proven detrimental by limiting customer choice and crippling the state’s once-vibrant solar industry,” the Hawaii Solar Energy Association said Wednesday in a report that said the industry’s outlook is “cloudy.”

The number of closed building permits for rooftop solar energy systems, representing projects that have been completed, was down 27.3 percent in August compared with the year-earlier month, HSEA said.