Hawaiian Electric’s residential customers will see lower bills in May than they did a year ago when the Russian invasion of Ukraine sent oil prices surging.

The state’s largest utility, which serves the entire state except for Kauai County, said Wednesday that the typical residential bill on Oahu this month is $6.54 lower than May 2022 but still about 9% higher than before oil prices spiked. Some of that increase is due to the discontinuation of burning lower-cost coal for power generation last year, Hawaiian Electric said.

Kauai, which gets its electricity through the Kauai Island Utility Cooperative, is owned by its members.

Hawaiian Electric said most of the reduction in residential bills can be attributed to prices stabilizing and declining in global oil markets in recent months.

On Oahu, a typical residential customer using 500 kilowatt-hours a month will pay $202.19 compared with $208.73 a year ago. Hawaii island customers will pay $221.83 compared with $241.26 for the same usage, while Maui island customers will pay $210.60 compared with $223.53.

Lanai customers using 400 kilowatt-hours a month will pay $195.65 compared with $226.35 a year ago while Molokai customers also using 400 kilowatt-hours a month will pay $198.42 compared with $205.10.

The state Public Utilities Commission regulates the formula for rates, which include fuel costs that fluctuate with world markets. Hawaiian Electric makes no profit on the fuels used to generate electricity. Under a fuel-cost risk-sharing regulatory mechanism, the company’s customers may be required to pay some of the cost when oil prices surge, resulting in a slightly lower rate for customers.

Hawaiian Electric said it expects the level of renewable resources on its grids by the end of the decade to reach at least 70% and better insulate customers from oil price volatility.

The company said an example of renewable energy’s benefits would be AES Corp.’s Waikoloa Solar + Storage project that came online in April and is providing lower-cost renewable energy to customers on Hawaii island. Hawaiian Electric said the project is expected to reduce typical residential bills for Hawaii island customers by about $5 a month starting in June.