The state Public Utilities Commission will allow seven community, environmental and industry groups as well as energy developers and government officials to have a greater say in whether building an undersea cable to connect the electrical grids of Oahu and Maui is in the public interest.

Allowing the "intervenors" to participate in the commission’s investigation will give authorities better information about the potential costs and benefits of such a project, according to a PUC ruling issued Tuesday.

When the PUC opened the investigation on July 11 it named Hawaiian Electric Co. and its affiliate Maui Electric Co., the state Energy Office, the state Department of Commerce and Consumer Affairs and the state Office of Consumer Advocacy as the main parties it would rely on to evaluate the need for an undersea cable.

In Tuesday’s ruling the PUC granted intervenor status sought by NextEra Energy Hawaii LLC, Life of the Land, the Renewable Energy Action Coalition of Hawaii, I Aloha Molokai, Maui County, Hawaii Interisland Cable LLC, and First Wind Holdings LLC.

These entities will be able to make official information requests of the main parties and have access to redacted information after signing nondisclosure agreements.

"This is great news for us," said Henry Curtis, executive director of Life of the Land, a Honolulu-based environmental and community-action group. The group opposes the cable, a proposal supported by former Gov. Linda Lingle and now by Gov. Neil Abercrombie.

"This gives us an opportunity to really investigate the cable. For the first time we can really understand all the aspects of the cable, technical, cultural, economic and environmental," Curtis said.

Estimates of the cost of an undersea transmission cable have varied widely over the years depending on its route and the source of the estimate. At one time a Lingle administration official estimated it would cost between $800 million and $1 billion to connect the islands of Maui County and Oahu. Since then state officials have been reluctant to provide cost estimates.

The PUC said the seven intervenors represent a "cross-section of interested stakeholders that are committed to assisting the commission in developing a sound docket record."

A July 11 decision by the PUC to investigate the need for an undersea tranmission cable was one of five orders it issued that day. In one of the other rulings, the commission opened a proceeding to review a proposal by Castle & Cooke Properties Inc. to build a 200-megawatt wind energy project on Lanai. In the ruling the PUC noted that a transfer of ownership of a majority stake in Lanai raised questions as to whether Castle & Cooke still had site control for its proposed project.

The PUC on Tuesday granted intervenor status in that case to a group that includes Life of the Land,  NextEra Energy Hawaii, Friends of Lanai, Hawaii Interisland Cable LLC, the Renewable Energy Action Coalition of Hawaii, Kaulana Kaho’ohalahala and Matthew Mano.