Electricity costs went up yesterday for O'ahu residents after Hawaiian Electric Co. implemented a 4.7 percent interim rate increase granted by the state Public Utilities Commission.

The increase applies to HECO's 294,000 customers and will generate $61 million in revenue annually, according to HECO. HECO said it needs the additional money to pay for major capital improvements and increased operating costs.

The typical residential household using 600 kilowatt-hours a month will see its monthly bill increase by $6.48 to $140.05.

The interim request was approved by the PUC last month, but the effective date was not set until yesterday. Still pending before the PUC is HECO's full rate increase request of 6.7 percent, which would raise company revenues by $86.8 million.

HECO spokesman Darren Pai said no timetable has been set for the full request.

"They have to do a very thorough review before they issue a final decision," Pai said. "We will be working with them and providing them with additional information as they conduct their review."

In addition to capital improvements, Pai said, revenue from the interim request will be used for operating costs, such as more frequent inspections of utility poles and lines, an increase in tree trimming around power lines, and an increase in servicing of power plants.

"We understand that there's never a good time for a rate increase and things are especially tough now," Pai said.

"However, we do have a responsibility and an obligation to meet the energy needs of our customers. This increase is for projects that are going to improve service, maintain our system and help us move towards our clean energy goals."