September residential electricity rates will rise in all counties except for Maui.

Hawaiian Electric Co. said the typical 600-kilowatt-hour bill for O'ahu residential customers will increase to $145.81 from $140.05 in August.

The effective rate for electricity in Honolulu is rising to 22.80 cents per kilowatt hour from 21.84 charged last month.

Hawaiian Electric said even with the increase for O'ahu, the rate is still below the 32.5 cents per kilowatt hour paid last September, when the effects of record-high oil prices were being felt.

Elsewhere in the state:

• Maui customers will see their rates decline to 25.16 cents from 25.55 cents that Maui Electric Co. charged residential customers in August.

• Big Island residential rates will rise to 31.93 cents from the 30.64 cents per kilowatt hour in August.

• Kaua'i Island Utility Cooperative's September rate is 32.03, or higher than the 30.74 cents last month.

Rates spiked in Hawai'i last year because most of the electricity is produced using petroleum products such as fuel oil or diesel oil, which rose in cost. Each month electricity rates vary in the state because of adjustments for fuel costs.

There typically is a lag between petroleum price increases because utilities must first use up inventory bought at different prices.

On O'ahu, rates peaked in September, when residential customers' monthly bill averaged $202.13.