Six months after it received approval for a $70 million rate hike, Hawaiian Electric Co. has told the state Public Utilities Commission that it may seek a new increase.

HECO filed a notice with the state regulatory agency last week that it may file a new rate request 60 days from now to help pay for its planned $164 million power plant in Kapolei.

If HECO seeks a rate hike it could take as long as a year to win regulatory approval.

The company didn't provide the amount of the proposed rate increase, saying it's still evaluating whether it will file a new rate case.

Lynne Unemori, HECO spokeswoman, said state law requires it to file such notices at least 60 days before it seeks to increase rates.

"It's still up in the air now," she said.

Hawai'i residents already pay the highest electricity rates in the nation. And those rates have risen steadily during the past year as fuel costs have soared.

HECO's last rate increase came in October when the PUC approved a 4.96 percent hike for the company's 293,000 customers on O'ahu.

The increase generated $70 million in new revenues for HECO but meant an increase of $6.61 a month for the typical local customer.