Hawaiian Electric Co. laid out its 30-year plan Friday to get the state to 100 percent renewable energy.

The electric utility said it would do this by installing a $340 million smart-grid infrastructure, building utility-scale wind and solar projects, increasing rooftop solar, using liquefied natural gas (LNG) as a bridge fuel, pursuing energy storage, building offshore wind, retiring old fossil fuel plants and possibly building a transmission line that would connect the renewable energy resources of neighbor islands.

In its 668-page filing, HECO made its third try to submit renewable-energy plans that the Public Utilities Commission would approve. The state agency rejected two previous drafts. In November the PUC said HECO’s second attempt fell short by not aggressively seeking access to lower-cost renewables, heavily relying on LNG. HECO’s initial power supply plan was filed in June 2013.

The utility lumped its three territories together — Oahu, Maui County and Hawaii island — to provide the renewable-energy portfolio. The breakdown:

>> 32.7 percent of the energy coming from private rooftop solar energy

>> 1.1 percent coming from feed-in-tariff solar

>> 23.3 percent coming from utility-scale solar

>> 14.2 percent coming from onshore wind

>> 21.4 percent coming from offshore wind

>> 0.5 percent coming from hydropower

>> 3.2 percent coming from geothermal

>> 3.6 percent coming from waste or biomass

HECO said the neighbor islands would lead the way to renewable-energy adoption, as Molokai and Lanai would reach 100 percent renewable-energy use by 2030, and Maui and Hawaii island would follow by 2040. Oahu would reach 100 percent by 2045.

The plan notes Oahu needs additional resources beyond what is available on the island. HECO said that means offshore wind, biofuels or a cable connecting the islands to transmit renewable energy to Oahu need to be considered.

“These alternatives need to be studied further in order to better understand their respective risk and relative costs,” HECO said. “Such endeavors require the efforts and input of our entire state, not just the utility.”

If the utility pursued the cable, HECO said it would look into creating a consolidated rate across its territories.

In November the PUC said it was concerned that HECO’s plans provide less benefit for ratepayers and instead favor the financial interests of the utility. The commission said in November that HECO had to update its LNG plans to take into account Gov. David Ige’s opposition to using it as a bridge fuel.

HECO didn’t back off its use of LNG. The electric utility said it needed the financial backing of NextEra Energy Inc., the company working to purchase HECO parent Hawaiian Electric Industries Inc., to convert its plants to allow the use of LNG.

The proposed $4.3 billion buyout needs PUC approval to close.

“HECO will shortly ask the PUC for approval of a contract to import LNG for electricity generation starting as soon as 2021 and ending by 2040,” HECO said.

The electrical utility said that if the PUC approves NextEra’s proposed purchase of HEI, the companies would enter into an agreement to acquire LNG from the Fortis LNG facility in Vancouver, British Columbia. HECO said delivery could start in 2021. LNG ultimately would be phased out to achieve 100 percent renewable energy, according to the plan.

HECO also said if NextEra’s buyout of its parent company is approved, the new owner would have HEI utilities getting 35 percent of their energy from renewable resources by 2020, 5 percent more than the state’s goal of 30 percent by that date. NextEra also would get the utilities to 50 percent of their energy from renewable resources by 2030, 10 percent more than the state’s goal. NextEra’s commitment would get the HECO companies to 70 percent of their energy coming from renewable resources by 2040 and 100 percent by 2045, in line with the state’s goals.

The PUC allowed 23 parties to participate in the docket. The utility held multiple stakeholder and technical conferences to share information and collect feedback from the parties.

Some of the groups involved critiqued the utility’s inclusion of liquefied natural gas in its third crack at the power plan.

“We applaud HECO for laying out a plan to achieve 100 percent renewable energy cost-effectively,” said Jeff Mikulina, executive director of Blue Planet Foundation. “But we don’t have to reach our clean-energy future by taking a detour through imported natural gas. Natural gas — composed mostly of methane — can be far more polluting than other fuels, and it comes with price risk.”

Mikulina said HECO “still missed the mark” in laying out a strategic role of the utility in a new energy landscape that includes electric vehicles, hydrogen storage and other technologies.

That was a similar issue the state agency had with the previous plan when sending HECO back to the drawing board in November. The PUC said the plan did not include any mention of many new technologies or strategies outside rooftop solar.

Isaac Moriwake, an Earthjustice attorney representing the Sierra Club, said the utility is more focused on using fossil fuels than adopting clean energy.

“On the third try, HECO’s ‘clean energy’ plan is still all about LNG, and it says LNG can only happen if NextEra takes over,” Moriwake said. “HECO and NextEra are focused more on maintaining the utility business of burning fossil fuels rather than accelerating real clean energy in Hawaii.”