Residential electrical rates fell on all islands in April except Oahu, the state’s two power companies reported.

The bill for an Oahu household using 600 kilowatt-hours of electricity a month is $212.05 in April, up $1.35 from March, according to Hawaiian Electric Co. The April rate is 33.8 cents a kilowatt-hour, up from 33.6 cents a kilowatt-hour in March.

HECO, its sister utilities in Hawaii and Maui counties, and the Kauai Island Utility Cooperative adjust their rates monthly to reflect changes in their fuel costs and the prices they pay for electricity purchased from independent power producers.

Maui Electric Co. customers are paying 36.5 cents a kilowatt-hour in April, down from 37 cents a kilowatt-hour last month. Hawaii island’s residential rate is 39.1 cents a kilowatt-hour, down from 39.5 cents a kilowatt-hour in December. On Kauai the rate is 41.8 cents a kilowatt-hour, down from 41.9 cents a kilowatt-hour in March.

The high cost of fuel oil used for power generation is a major reason why the price of electricity in Hawaii is more than three times the national average. Hawaii residents paid an average of 37.4 cents a kilowatt-hour for electricity in January compared with the national average of 11.7 cents a kilowatt-hour, according to the latest data available from the U.S. Energy Information Administration.

Roughly 80 percent of the electricity consumed in Hawaii is generated by burning oil, the highest percentage of any state. The next-highest state is Alaska at about 14 percent, according to the EIA.

Hawaii’s two electric utilities last year burned 7.21 million barrels of oil at an average cost of $127.83 a barrel to meet the state’s electricity needs, according to data compiled by the state Department of Business, Economic Development and Tourism. That compared with 7.61 barrels of oil in 2012 at an average cost of $135.38 a barrel.