Hawaii has long been a national leader in solar energy production, but the state is lagging in a quest to reach a renewable-energy frontier that appeared to be on the horizon several years ago.

A federal agency regulating development of offshore wind farms has issued 16 ocean leases for such projects off eight coastal states since 2012.

The state surrounded by the ocean, however, isn’t among them.

Furthermore, a Massachusetts project with one of the leases last month received the first go-ahead for construction and operation of a large-scale offshore U.S. wind farm, while the same thing in Hawaii is estimated to be more than a decade away.

Offshore wind energy has been touted as a big piece for reaching a state goal to generate 100% of energy from renewable sources by 2045 while also reducing the cost of electricity for consumers and businesses.

Reaching this goal is particularly challenging on Oahu, according to the Hawaii State Energy Office, which regards wind as the second most abundant renewable energy resource in the state behind geothermal power.

“Oahu’s limited land, diverse land use needs, and high electricity consumption make it the most challenging of all the Hawaiian Islands to reach 100% renewable energy,” Kirsten Baumgart Turner, the agency’s deputy energy officer, said in an email.

Much of the potential from wind energy is seen as being offshore because wind farms on land have run into resistance largely over proximity to populated areas and unsightliness.

Because wind farms out to sea can be a dozen or more miles away, view issues become reduced and projects can be far larger.

For instance, the Na Pua Makani wind farm in Kahuku, which has sparked efforts at the Honolulu City Council to require future terrestrial wind farm siting be as much as 5 miles from neighboring property lines, has a 24-megawatt capacity while single projects contemplated off Oahu have been 400 megawatts.

A project that size could generate enough electricity to power nearly 25% of the island where oil and coal still account for 74% of energy production through Hawaiian Electric.

With such potential, much effort has been made to tap offshore wind energy for Oahu, including task force meetings that began in 2012, regulatory work, public hearings and developer proposals.

Yet the initiative seems caught in the doldrums.

Jens Borsting Petersen, managing director of Alpha Wind Energy, a Danish- based company that sought two leases in 2015 from the U.S. Bureau of Ocean Energy Management to establish wind farms off Oahu’s northwest and south shores, said it appears the regulatory process has been stuck for five years waiting for BOEM to bring various government agencies into alignment on how to move forward.

“I am hopeful this will happen in the near term, but I have no facts that support a definable timeline,” he said in an email.

Alpha Wind proposed developing 816 megawatts of wind power using 51 turbines 17 miles south of Diamond Head and 51 turbines 12 miles northwest of Kaena Point.

Another company, Oregon- based Progression Energy LLC, proposed a 400-megawatt project off Oahu’s South Shore but recently shifted its plan to windward waters after saying that the Department of Defense expressed concerns about a South Shore wind farm interfering with military training, readiness and national defense.

Company officials recently forecast that it may be around two years before BOEM grants any Hawaii leases, and that the need for engineering, environmental and other studies after that could mean construction happening in 2032.

“The project is still very far out,” Austin Kino, community outreach coordinator for Progression’s proposed project, told the Kaneohe Neighborhood Board at a meeting earlier this month.

John Romero, BOEM public affairs officer, said the agency has no estimated timetable for providing an ocean lease for wind energy production off Oahu in federal waters, which begin 3 nautical miles from shore.

Under federal regulations BOEM must auction a lease if more than one qualified developer is interested.

For Hawaii, Alpha Wind and Progression submitted unsolicited lease applications in 2015 while two other companies, including a Norwegian-based energy firm now known as Equinor ASA, expressed interest.

Since then BOEM has been working to identify and formally designate appropriate areas for wind energy production off Oahu based on best available science and information from stakeholders including local communities, the state and the Department of Defense.

The process included multiple public meetings held in 2016 where concerns were raised on issues including impacts on views out to sea, marine life and fishing. Area selection is not yet finalized.

Most recently, BOEM has funded research by the National Renewable Energy Laboratory to better evaluate costs for wind farm development off Oahu. A cost analysis report is expected in October.

Meanwhile, other coastal states have leases and are far ahead with projects.

In Virginia, utility company Dominion Energy was awarded an offshore lease in 2013 and has two turbines — the first installed in U.S. federal waters — operating as a 12-megawatt pilot project powering up to 3,000 homes. The company anticipates completing a 2,640-megawatt network of turbines 27 miles off Virginia Beach capable of powering up to 600,000 homes in 2026.

Massachusetts in May laid claim to having the first approved large-scale commercial offshore wind farm project: an estimated $3 billion venture with 62 turbines capable of producing 800 megawatts and located 15 miles off Martha’s Vineyard.

This project, called Vineyard Wind 1, received an ocean lease in 2015, followed by a federal “record of decision” approval May 11 for its construction and operations plan that was reviewed by more than two dozen federal, state and local agencies over more than 3-1/2 years.

“With this record of decision on Vineyard Wind on the books, the era of American offshore wind is no longer on the horizon — it’s here, now, off the coast of Massachusetts, and the answer to America’s energy future is blowing in the offshore wind,” U.S. Sen. Edward Markey said in a written announcement from the project’s private developer. “Vineyard Wind will be the first of many offshore wind projects to come, and we can use our Bay State know-how to show the rest of the country how to get steel in the water, zero-emission energy on the grid, and union jobs to American workers.”

The project’s developer projects that power will begin flowing in 2023 and that electricity ratepayers will save $1.4 billion over the first 20 years while carbon emissions are reduced by more than 1.6 million tons annually.