State regulators gave final approval for a 5.7 percent Hawaiian Electric Co. rate hike, most of which had been in effect on an interim basis for more than a year.

HECO previously had received interim approval for the increase in two phases. Customers began paying most of the increase in August 2009, and the remainder in February 2010, HECO said.

The Public Utilities Commission gave final approval to the rate hike yesterday, making a few minor changes to the interim decisions that will result in a small refund for customers. The typical residential customer using 600 kilowatt hours of electricity a month will receive a refund of 11 cents plus interest.

The rate hike has generated an additional $74 milion in revenue for HECO to help pay for more than $375 million in investments, including the utility’s new Campbell Industrial Park generating station that is fueled by rewnewable biodiesel.