The state Public Utilities Commission has accepted an updated plan submitted by Hawaiian Electric Cos. detailing how it will reach the state’s goal of 100 percent renewable energy five years ahead of schedule.

A key goal of the Power Supply Improvement Plan involves acquiring nearly 400 megawatts of new renewable energy resources by 2021. That would represent about one-third of the capacity of the three generating plants that the company currently operates on Oahu: Waiau, Kahe and Campbell Industrial Park.

“Collectively, this represents the largest new generation procurement ever undertaken in the state,” the PUC said in its decision Friday that was made public Monday. “There is broad stakeholder support for acquiring new renewable resources, as well as significant developer interest in meeting Hawaii’s needs.”

The PUC urged the utilities to move quickly on a “transparent, timely and successful procurement process” to work with project developers and capture federal investment tax credits before they expire.

To help the utilities get to the 100 percent level, they are going to need to add utility-scale solar, customer-­sited batteries, rooftop solar, wind and biofuels. HECO expects private solar systems to more than double by 2030 to 165,000 from the 79,000 now in use across HECO’s territories.

“After 2022, coal won’t be burned to generate electricity on Oahu anymore,” Hawaiian Electric spokes­­woman Shannon Tangonan said. “It’s the cheapest power source by a significant margin, and it’s the largest generator of firm, 24/7 power on the island. It’s also a major contributor to the emissions that are causing climate change.

“That capacity has to be replaced with a combination of intermittent renewables like solar and wind as well as firm generation that can run on biofuels. Those resources have to be built, and we have to pay for the power they generate or the fuel they use and in none of our projections are they cheaper than what we’re paying for coal.”

The PUC, which accepted the fourth version of Hawaiian Electric Cos.’ power supply plan, said in its review that the commission “has reasonable assurance that many of the actions identified … are credible, supported by sound judgment and analysis, informed by stakeholder input and consistent with state energy policy and prior commission orders.”

Hawaiian Electric Cos. forecast that its three sister utilities — Hawaiian Electric Co. on Oahu, Maui Electric Co. and Hawaii Electric Light Co. on Hawaii island — would exceed the state’s renewable-energy milestones in 2020, 2030 and 2040. Hawaiian Electric Cos. projects that the renewable portfolio standard will be at 48 percent by the end of 2020, beating the mandated goal of 30 percent; at least 72 percent by the end of 2030, topping the mandated goal of 40 percent; and 100 percent by the end of 2040, surpassing the mandated goal of 70 percent.

“We appreciate the commission’s acceptance of our plan and its guidance for moving forward,” Hawaiian Electric President and CEO Alan Oshima said.

Hawaiian Electric Cos. forecast in its plan that by 2020 Hawaii island would reach a renewable portfolio standard of 80 percent; Maui, 63 percent; Lanai, 59 percent; and Oahu, 40 percent, and that MECO was working with the Molokai community on options to achieve 100 percent by 2020.