Hawaii island residents’ electrical bills are set to rise nearly $5 after the state approved Hawaii Electric Light Co.’s request to increase rates.

On Monday the state Public Utilities Commission said in an “interim” decision that HELCO is allowed to increase rates by $9.94 million, or 3.4 percent. The approved increase will boost a typical bill for residential customers using 500 kilowatt-hours by $4.98, to roughly $167.56. The average monthly residential bill over the past year has been $162.58.

The interim decision is one step in the rate-making process. HELCO can apply the interim rates once it gets additional approval from the PUC. The utility has to file a detailed outline of the new rates with the PUC, and the agency has to approve the language for the interim rates to go into effect.

HELCO said Tuesday the rate increase will help support its progress in bringing on more renewable energy resources.

Out of Hawaiian Electric Industries’ three utilities — Hawaiian Electric Co., Maui Electric Co. and HELCO — the Big Island utility leads in the use of renewable resources to generate electricity. HELCO said the company increased the use of renewables to make up 57 percent of its energy mix as of June. In 2010 renewables made up 35 percent of HELCO’s energy mix. The Big Island utility’s energy portfolio is made up of oil, wind, solar, geothermal and hydropower.

The utility said the increase in rates also will help pay for grid upgrades and vegetation management. HELCO said it has spent more than $14 million on tree trimming and removal, as it focuses on areas where non-native albizia trees “threaten utility equipment and highways.”

The approved rate increase is roughly half of what the electrical utility originally requested.

In September HELCO asked for a base rate increase of $19.3 million, or 6.5 percent. A typical residential customer on Hawaii island using 500 kilowatt-­hours per month would have seen a $9.31 monthly bill increase.

Regulators could rule differently in the final decision. If the PUC decides in its final decision to approve lower rates than the interim, HELCO must refund customers the difference with interest. If a higher amount is approved, the increase will be applied only from the time it is approved, not retroactively.

There is no deadline for the PUC to issue a final ruling, but PUC Chairman Randy Iwase said he plans to issue a final decision before the end of 2017.

“I don’t expect it to be lengthy process,” Iwase said. “We have the information that has been submitted thus far. … I hope we will be able to render a decision by the end of the year.”

Iwase said the PUC’s interim decision for HELCO is not a sign of how the agency will rule on other electrical utility rate cases.

“It does not portend what we will do to the HECO case and the MECO case when it is filed or any other utility case,” Iwase said. “We have to take each one on a case-by-case (and) fact-by-fact basis.”

PUC is currently reviewing a request to increase rates for electrical utility customers on Oahu.

In December HECO requested to increase rates 6.9 percent, or $106 million annually. If approved, customers’ electrical costs would rise by $8.71 a month based on December bills. The average bill for an Oahu household using 500 kilowatt-­­­ hours in December was $132.32.