Residential electricity rates on Oahu rose in January from December, the first increase in three months, according to Hawaiian Electric Co.

A 600-kilowatt-hour bill for Oahu residential customers climbed to $200.91 this month from $195.38 in December.

The effective rate for electricity on Oahu this month is 32 cents a kilowatt-hour, up from 31.1 cents a kilowatt-hour last month.

HECO adjusts its rates monthly primarily due to fluctuations in the price of fuel oil it uses for power generation. The utility estimates that about 73 percent of the electricity generated or purchased by HECO and its subsidiaries last year was produced with fossil fuel.

HECO is required by law to reduce its reliance on fossil fuel so that 40 percent of its electricity production is from renewable sources by 2030.

Before January’s increase, electric rates on Oahu had fallen in November and December. Oahu electric rates had been as high as 35.1 cents a kilowatt-hour in June 2012.

Elsewhere in the state:

» Maui Electric Co. customers saw their rate fall to 38.4 cents per kilowatt-hour this month from 39.5 cents in December. The typical Maui bill fell by $6.89 to $238.96.

» Hawaii island’s residential rate rose to 39.0 cents a kilowatt-hour from last month’s 38.7 cents. The typical bill rose to $244.72 from $242.46.

» On Kauai, the rate fell to 41.6 cents per kilowatt-hour from 42.6 cents in December, according to the Kauai Island Utility Cooperative.

Hawaii has the highest electric rates in the nation. The statewide average of 36.87 cents a kilowatt-hour in October was triple the national average of 12.03 cents a kilowatt-hour, according to the most recent numbers available from the U.S. Energy Information Administration.

Louisiana had the lowest average rate at 8.67 cents a kilowatt-hour.