Hawaiian Electric Co. has contracted to build the state’s largest solar farm near Haleiwa with up to 500,000 solar panels on 100 acres.

Houston-based NRG Energy Inc. will build the solar farm, which will have sheep grazing on the grass under the panels.

The Haleiwa solar farm, known as Kawailoa Solar, is one of three being built by NRG on Oahu. Together the three will boost Oahu’s renewable electric output by 3 percentage points. Currently, renewable energy makes up 19.4 percent of Oahu’s fuel mix.

“Reaching this agreement on Kawailoa Solar is another big step in our renewable energy plans for Oahu,” said Alan Oshima, HECO president and CEO, in a prepared statement.

HECO will buy the power from NRG at a discount to the price previously negotiated with a company that started the project. Maryland Heights, Mo.-based SunEdison got the ball rolling on the three solar farms before it ran into financial problems and eventually filed for bankruptcy a year ago.

HECO submitted an application Monday with state regulators to buy power from NRG’s 49-megawatt Kawailoa Solar farm for 11 cents a kilowatt-hour. SunEdison was going to charge HECO 13.5 cents a kilowatt-hour. Both contracts are for 22 years.

In addition to Kawailoa Solar, NRG plans to sell solar power produced at its 14.7-megawatt Lanikuhana Solar plant to HECO for 11.4 cents per kilowatt-hour and for 10.4 cents per kWh from the 45.9-megawatt Waipio Solar. SunEdison was going to charge 13.5 cents at those two solar farms as well.

HECO said the prices depend on the projects qualifying for a state tax credit. Hawaii offers a 35 percent tax credit off the total cost of the solar system. It is capped at $500,000 for each commercial system.

Currently the largest solar farm operating in the state is the 27.6-megawatt Waianae Solar. San Diego- based Eurus Energy America Corp., owner of the facility, announced in January the West Oahu project was online.

The three NRG solar projects have the combined capacity to power more than 17,974 homes at peak, with a total of 109.6 megawatts of solar generation.

The HECO contract with the proposed solar farms must be approved by the state Public Utilities Commission.

When SunEdison ran into financial trouble, HECO decided to terminate the contract for the three solar farms. At the time, Randy Iwase, PUC chairman, chastised HECO’s decision because of the amount of renewable energy lost. Iwase declined to comment Monday on the new contracts with NRG because they’re being reviewed by the PUC.

Craig Cornelius, president of renewables at NRG, said once his company bought the farms from SunEdison in November, HECO was quickly working to secure the contracts.

“We closed on the assets, and 45 minutes later we walked into a meeting with Alan (Oshima) and the HECO team,” Cornelius said. “Their team and ours have been incredibly focused to get this project on the rails.”

All three projects are targeted to come online in 2019.

Wren Wescoatt, energy development consultant for NRG, said the company has not decided on the type of panels that would be installed at Kawailoa. Depending on the type, the 100 acres in Haleiwa could host from 150,000 to 500,000 solar panels.

After speaking with different community members, Cornelius said NRG decided to plan for each of the three solar facilities to be sites where local ranchers are able to graze Dorper sheep, which are raised for their meat.

“It’s helpful for the solar facility because vegetation control is pretty critical to operate these facilities,” he said. “There is a little bit of a symbiotic relationship there that we’re able to have.”

Cornelius said he would like to build more NRG projects in the state.

“We’re glad to be moving those three down the line and eventually some other ones that come down behind them,” he said.