Hawaiian Electric Co. customers saw a small discount in September as oil prices dipped.

The bill for a typical household using 500 kilowatt-hours on Oahu is $133.98 this month, 75 cents lower than what customers paid in August, when it was $134.73. The price per kWh on Oahu is 24.8 cents, down from 24.9 cents in August.

HECO spokesman Darren Pai said bills were lower due to lower fuel costs.

“Most of our customers are seeing slightly lower bills due to lower fuel costs, which is always welcome news,” Pai said.

The price of benchmark West Texas Intermediate crude oil dropped from $50 a barrel in July to $40 in the beginning of August. The price has climbed back up in September, and was quoted at $44.90 a barrel on Tuesday.

September’s lower bills end a streak of three monthly increases as fuel prices climbed.

The bill for a typical household on Oahu in August was $1.30 higher than in July. For the month of July, the electric bill was $4.09 higher than what customers paid in June. Oahu’s June bill was $4.49 higher than what customers paid in May, when the typical household bill was $124.85.

Hawaii has the highest electricity rates in the United States, due in part to the state’s use of imported oil for most of its power.

In 2015 oil made up roughly 71.1 percent of HECO’s energy mix on Oahu. It made up roughly 62.5 percent of the energy mix at Hawaii Electric Light Co. on the Big Island and 73 percent of the energy mix at Maui Electric Co. HECO imports oil mainly from Southeast Asia and the Middle East. Other states use energy resources such as natural gas, hydroelectric power, coal or nuclear power.

The price of electricity in the state is more than double the national average, according to the latest figures from the U.S. Energy Information Administration. Hawaii residents paid an average of 27.5 cents a kWh in June; the national average was 12.7 cents a kWh in the same month.

Neighbor islands changes were mixed.

The residential rate for HELCO customers on Hawaii island was 30 cents a kWh. The average bill this month for a household using 500 kWh on the Big Island is $161.85, up from $161.67.

Maui customers paid 27.2 cents per kWh, down from 28.1 cents in August. The average bill for a household using 500 kWh is $145.42, down from $149.89, last month.

Maui Electric Co. customers on Molokai using 400 kilowatt-hours of electricity are paying an average of $133.35, with a rate of 31 cents a kWh, up from August, when the typical bill was $133.11.

On Lanai bills were down.

Those using 400 kWh of electricity on Lanai are paying 31.7 cents a kWh. Lanai residents are paying $136.43 in September, compared with $138.17 in August.

The typical customer bill on Lanai and Molokai is measured with electrical use at 400 kWh due to lower energy use, HECO said.

HECO, MECO and HELCO monthly bills include the cost for kWh used plus other charges.

The Kauai Island Utility Cooperative decreased its rate to 31.95 cents a kWh in September, down from 32.71 cents in August. The average bill for a household using 500 kWh of electricity, including a $10.58 customer base charge, is $170.33, down from $174.13.