KAHULUI, Maui — Vision met reality on the first day of the Maui Energy Conference, which featured a series of panel discussions on how Hawaii can — or can’t — reach its goal of getting 100 percent of its electricity from renewable sources by 2045.

“The sheer infrastructure and scope that would be required to go to 100 percent on Oahu is really impossible under today’s technology,” Kauai Island Utility Cooperative CEO David Bissell said Wednesday at the Maui Arts and Cultural Center.

“There’s just not enough land there,” he said. “It’s got to come from biofuel or other technology or from other islands.”

That’s Oahu, home to nearly 1 million people and a city full of neon lights. Kauai, a rural island of 65,000 residents, could reach the state’s goal within the next 30 years and is already 40 percent of the way there, Bissell said.

But closing that gap could come at a significant cost even on Kauai, he said.

Bissell estimated that it would take 5,000 acres and a $1 billion investment, with debt-service payments of up to $70 million, for Kauai to be 100 percent renewable under today’s technologies. KIUC has roughly 35,000 member customers.

He said a recent modeling exercise was “a real eye-opener” to him. To make it pencil out, he assumed more than three times as many rooftop solar systems, battery storage infrastructure and agricultural land for utility-scale photovoltaics and biomass crops.

“We wouldn’t be subject to as much volatility, but it really wouldn’t have a downward pressure on rates,” he said.

Hawaii Gov. David Ige signed the 100 percent renewable energy goal into law last year, and the Legislature is fine-tuning the policy this session. The path forward remains uncertain, but there is agreement that the status quo won’t cut it.

“No one is going to get to 100 percent without upending the utility model,” said former Colorado Gov. Bill Ritter, now a director at the Center for the New Energy Economy at Colorado State University.

He considers Hawaii’s 100 percent renewable energy objective to be realistic.

“It’s absolutely doable,” Ritter said. “It’s part of what the future of the world needs to look like.”

Utility executives said they support the 100 percent goal and are willing to adapt, but underscored the practical limitations of the current technologies and how the regulatory environment slows the process.

Hawaii Gas CEO Alicia Moy and Hawaiian Electric Vice President Shelee Kimura reiterated their support at the conference for using liquefied natural gas as a bridge fuel to get to a 100 percent renewable future.

“Just because it’s a fossil fuel doesn’t mean we shouldn’t be considering a cleaner version of that to get to our end state,” Moy said.

Ige came out against LNG for electricity in August and has not backed down. He has said investments in LNG infrastructure would be better spent on renewable energy projects.

Bissell said the governor’s stance prompted Kauai — the only county not powered by investor-owned subsidiaries of Hawaiian Electric Industries — to look at propane instead.

He explained that as the head of a member-owned cooperative, he’s directly accountable to an elected board of directors. Given how environmentally conscious Kauai residents are, he said he has to keep them happy if he wants to keep his job.

Kimura said if the state is going renewable because it’s trying to be environmentally responsible, the disposal of renewable energy systems is going to be increasingly important.

Ritter and other out-of-state speakers at the conference, such as Kristen Mayes, senior sustainability scholar at Arizona State University, took the opportunity to remind people that while there are challenges in achieving the state’s ambitious energy goals and differing perspectives on how to get there, Hawaii is leading the country in many ways, like integrating rooftop solar into the grid.

“You have so, so much to be proud of,” Mayes said.

The conference continues Thursday with discussions about how the regulatory and governmental framework helps or hinders energy investments in Hawaii, among other topics. Two of the three members of the state Public Utilities Commission will be panelists.