Residential electricity rates fell in August on all islands except for Kauai.

Hawaiian Electric Co. said a typical 600-kilowatt-hour bill for Oahu residential customers fell by $1.20 to $215.65 in August from $216.85 in July. The effective rate for electricity in Honolulu is 34.5 cents per kilowatt-hour declined to 34.5 cents a kilowatt hour from 34.7 cents a kilowatt hour.

Elsewhere in the state:

— Maui Electric Co. customers saw rates fall to 35.4 cents per kilowatt-hour this month from 37.5 cents in July. The typical Maui bill fell by $12.26 to $221.30.

— Hawaii island residential rates fell to 40.1 cents a kilowatt-hour from last month’s 41.4 cents. The typical bill fell by $7.86 to $250.82.

— On Kauai, the rate rose to 40 cents per kilowatt-hour. Last month the rate charged by the Kauai Island Utility Cooperative was  38.4 cents per kilowatt-hour.

HECO and KIUC adjust their rates monthly largely to reflect changes in fuel costs. The utilities generate 75 percent of their electricity from petroleum, making the them vulnerable to swings in oil prices.