Hawaiian Electric Co. said Thursday it is beginning to see customers line up for the only rooftop solar option left.

As of Tuesday, Hawaiian Electric Co. and its sister companies — Maui Electric Co. and Hawaii Electric Light Co. on Hawaii island — had received 234 applications for the “self-supply” solar program.

With a self-supply system a homeowner cannot send excess solar to the grid for credit, but can draw power from the grid. Most self-supply systems include a battery to store power during daylight hours and use at night or in cloudy conditions.

Self-supply applications are up from only about 50 in early October.

“Things are just getting started,” said Jim Alberts, Hawaiian Electric senior vice president of customer service, in a prepared statement. “Solar power is still a viable option and we expect more customers to install self-supply systems as they learn more about the program.”

Chris DeBone, principal at Hawaii Energy Connection, said some self-supply systems can start at $5,000 after tax credits. DeBone said the systems cover roughly 30 percent of a home’s energy demand and that customers can add batteries over the years to increase the system size.

Before tax credits, the total upfront costs range from $14,000 for a system without batteries to upward of $35,000 for a system that includes batteries, DeBone said.

There is a 35 percent state tax credit for solar, with a cap of $5,000, and a federal 30 percent tax credit. There is no state tax credit for batteries.

“In 2008 the cost of PV alone was the same price as PV plus storage,” DeBone said.

Colin Yost, principal at RevoluSun, said that he has noticed customer interest in self-supply perk up but that residents should have more than one option.

“Self-supply is improving, but it’s still good to have more than one choice,” Yost said.

Self-supply has been an option for residents since the state Public Utilities Commission created it more than a year ago, but it recently became the only option for new solar owners.

The state ended its popular Net Energy Metering solar program in October 2015, replacing it with self-supply and another program called grid-supply. The original NEM program credits customers the full retail rate for excess energy their solar systems send to HECO’s grid.

All of HECO’s service territories have met the state’s limit placed on grid-supply. The program lets customers export excess energy to the grid and credits owners 15 cents a kilowatt-hour for the energy their systems send. The rate is roughly 8 cents less than the retail rate that had been offered through the NEM program.

DeBone said his company didn’t offer self-supply options until after grid-supply met the cap.

“It just made no sense,” DeBone said. “Of course, there is going to be an uptick now because grid-supply is over.”

Self-supply was the least attractive of the programs because some homes would require batteries, making the payback period longer than the other two programs.

Self-supply’s payback period is roughly seven to eight years, Yost said.

“Costs have been going down,” Yost said. “It just depends on what type of equipment people are using.”

Net-energy-metering customers are able to recoup their investment in about four years.

The payback time for grid-supply is five to seven years, Yost said.

HECO said nearly 100 self-supply applications have been approved and are ready for installation. The other applications are going through a standard technical review.