Hawaiian Electric Co.'s residential customers on O'ahu are getting a slight break this month on their energy bills courtesy of falling oil prices.

The utility says its typical residential customer will see their bill drop to $182.01 from the $196.52 they were billed in October.

The $14.51 decline represents a 7.4 percent drop. The bill is based on a household that uses 600 kilowatt-hours each month.

That should be welcome news for many people who have seen their electrical bills steadily rise as the price of crude oil surged this year, along with their gasoline tab and higher costs from shipping surcharges tied to petroleum costs.

Hawai'i residents have the highest average statewide electricity rates in the U.S., paying almost three times the national average. HECO said more cuts could be in order given oil's decline in recent months.

"Our hope and expectation is that it will drop further in December," said HECO spokesman Peter Rosegg.

Hawai'i's electricity prices are heavily tied to the price of petroleum because most of the electrical generators in the state run on fuel oil. That's different than most of the country where coal and nuclear energy dominate electrical generation.

Thus, electricity rates have been rising here as crude oil spiked, reaching a high of $147.27 a barrel on July 11. As of yesterday the price of crude had fallen to $61.04 on the New York Mercantile Exchange, a 59 percent drop since the top of the market.

HECO passes through increases in fuel oil costs to consumers in something that's called the Energy Cost Adjustment clause on its bills.

But electricity prices haven't fallen by as much or as fast for several reasons, including that the price for fuel oil that HECO uses peaked at a later date.

HECO must also use up a 30- to 60-day supply of fuel oil bought at higher prices before the falling prices start showing up in monthly billings. People have been asking when the lower crude oil costs will show up in their utility bills, especially since gasoline prices have been plummeting.

The decline began last month when HECO's effective rate came down from September's peak price of 32.5 cents per kilowatt-hour.

In October, the effective rate dropped to 31.3 cents.

In November, the rate fell to 28.9 cents, the lowest in five months.

HECO noted that while it uses the effective electricity rate to discuss how bills are rising or falling, customers won't get similar numbers when they divide their kilowatt-hour usage into the total amount due listed on the bills.

A Makiki resident recently did that and found the cost per kilowatt-hour was higher than what HECO had released.

Rosegg said HECO's bills include a fixed "customer charge" of $8 a month that's not included in computing the effective kilowatt-hour cost. He said by excluding this, HECO can come up with a per kilowatt-hour cost that applies to all residential customers, no matter how much electricity they use.

A kilowatt-hour is when 1,000 watts are used for one hour.