Residential electrical rates on Oahu rose in January to their highest level in nearly a year as a result of Hawaiian Electric Co. taking some of its more efficient generating stations out of service for maintenance.

The bill for a typical household using 600 kilowatt-hours of electricity a month is $211.22 in January, $5.02 more than in December, according to HECO. The January rate is 33.7 cents a kilowatt-hour, the highest since 34.9 cents a kilowatt-hour in March 2013.

Although the price of fuel used for generation fell in January, the decline was more than offset by higher costs associated with removing the more efficient generators from service, said Peter Rosegg, company spokesman.

"Maintenance is part of the operation of any piece of machinery, and a generator and its auxiliary equipment are a complex system. We schedule regular maintenance to have as little impact as possible on customer bills. But inevitably there are times when highly efficient generators need work," Rosegg said.

He also said HECO is still on track to deactivate its Honolulu Power Plant at the end of this month. The deactivation of the oil-burning plant, which went into service in 1954, is possible partly because of the growth of renewable energy, according to HECO.

Elsewhere inthe state, electrical rates declined in Maui County and on Hawaii island but rose on Kauai.

Maui Electric Co. customers are paying 35.7 cents per kilowatt-hour in January, down from 36.9 cents a kilowatt-hour last month. Hawaii island’s residential rate is 39.5 cents a kilowatt-hour, down from 40.6 cents a kilowatt-hour in December. On Kauai the rate is 42.3 cents a kilowatt-hour, up from 41.2 cents a kilowatt-hour in December.

The high cost of fuel oil used for power generation is a major reason why the price of electricity in Hawaii is nearly three times the national average. Hawaii residents paid an average of 37.2 cents a kilowatt-hour for electricity in November compared with the national average of 12.1 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.