Hawaiian Electric Co. was sent back to the drawing board on its $340 million smart-grid plan by state regulators.

The Public Utilities Commission dismissed Hawaiian Electric Co.’s smart-grid application Wednesday, ordering the electrical utility to submit a more detailed plan in June. The panel had concerns about the cost of the plan and lack of details.

“The commission is concerned that the companies’ smart grid strategy and roadmap … does not provide the level of specificity and detail necessary to fully evaluate the merit and value of the overall approach,” the PUC said in the order.

In March, HECO said its $340 million Smart Grid Foundation Project would include a wireless communication network, smart meters and enhanced technology that would upgrade the existing electric grid to be more automated and energy-efficient.

The PUC ordered HECO to submit a new detailed grid modernization strategy for each of its three utilities no later than June 30. HECO must brief the commission in April on the approach and content of the draft.

“A modernized grid is the ‘backbone’ necessary to advance the state’s (renewable energy) goals, support integration of additional levels of renewables, encourage competition, empower consumers to make their own choices concerning the level and type of electric service they desire and average customer-sited resources to assist in grid operation,” the PUC said.

HECO spokesman Darren Pai said that the electrical utility will work with stakeholders to develop plans to modernize its electric grid in its three service territories.

“We all want to get this right,” he said. “Modernizing the electric systems on five islands — essentially moving from analog to digital — is a big, complex, multiyear project involving rapidly changing technology. We are still committed to building a high-tech grid that’s efficient, reliable and cost-effective.”

Pai said the utility plans to be at 48 percent renewable by 2020, and the technology of the smart grid is necessary to balance the power supply.

“With the continued growth of private solar energy systems, at some point soon we’ll have 100,000 individual power generators online across Hawaii,” he said. “We need real-time data and leading-edge technology to balance power supply and demand to keep the grid stable and running as efficiently as possible.”

Pai said the utility’s timeline for renewable-energy adoption has not been changed by the PUC dismissing the smart-grid plans.