Residential electric rates on Oahu are little changed in July compared with June, Hawaiian Electric Co. reported Friday.

Elsewhere around the state, power bills fell in July on all islands except Kauai.

The bill for a typical household on Oahu using 600 kilowatt-hours of electricity a month is $204.27 in July compared with $204.47 in June, according to HECO.

The residential rate on Oahu eased to 32.5 cents per kilowatt-hour in July from 32.6 cents per kilowatt-hour in June. The July rate also was lower than the same month last year, when residential customers paid 34.7 cents a kilowatt-hour.

The monthly changes in electric rates charged by HECO, its subsidiary utilities and the Kauai Island Utility Cooperative are mainly the result of changes in the price of fuel oil, which is used to generate about 75 percent of the electricity consumed in the state.

The reliance on oil for power generation is one of the primary reasons electricity in Hawaii is more than three times the national average. Hawaii residents paid an average of 36.9 cents a kilowatt-hour for electricity in April compared with the national average of 11.9 cents a kilowatt-hour, according to the latest data available from the U.S. Energy Information Administration.

Topping the state in July was Kauai, where residents paid 42.3 cents a kilowatt-hour for electricity, up from 41.5 cents a kilowatt-hour in June.

Maui Electric Co. customers saw their rate decline to 36.1 cents per kilowatt-hour from 36.9 cents per kilowatt-hour last month. The typical Maui bill fell $4.87 to $225.48.

Hawaii island’s residential rate fell to 39.2 cents a kilowatt-hour from last month’s 39.8 cents. The typical bill fell to $245.57 from $249.02.

The state Public Utilities Commission recently took HECO and its subsidiaries to task for not doing more to address high electrical rates. The PUC on May 31 issued three orders affecting rates and the rate-setting process, including one directing Maui Electric Co. to refund ratepayers more than $8 million.

Another order initiated a PUC investigation of HECO’s new rate-setting mechanism known as “decoupling” instituted by the utility in 2010. Decoupling is designed to encourage the development of renewable energy and energy conservation by eliminating the economic incentive on the part of the utility to sell more electricity.

However, the PUC commissioners said they wanted to re-examine the initiative to “ensure that these mechanisms do not insulate the HECO companies from making timely and necessary improvements to their business models, strategies and operational practices to serve customers and the public interest.”