Hawaiian Electric Co.'s proposed 7.2 percent rate increase is a departure from past rate hikes in that the increase wouldn't be applied to all residential customers equally.

The company is proposing a tiered rate scale under which households using the most electricity will face a 12 percent rate hike, while those who use the least amount will only see a 3 percent increase.

The tiered structure is similar to one proposed last year by HECO's sister company, Hawaii Electric Light Co., and helps fulfill the utilities' desire to slow O'ahu's increasing appetite for energy by promoting conservation.

The utility said under the tiered plan the majority of residential customers would see an increase of 3 percent to 6 percent.

For example, a customer that only uses 350 kilowatt hours a month would have a 3.4 percent rate increase.

The typical O'ahu household using 600 kilowatt hours would get a 6.1 percent rise.

A home using 1,250 kilowatt hours would have a 8.3 percent climb in rates.

HECO spokeswoman Lynne Unemori said the utility has realized that some poorer households could face the highest rate increase and is mulling a provision to cap rates for certain low-income customers.

The company also wants to implement a voluntary program that grants discounts for residential electrical use during off-peak hours while charging premiums for use during peak and "midpeak" hours.

If you sign up for the program, you get a discount of 3.5 cents a kilowatt hour for electricity during the off-peak hours of 9 p.m. to 7 a.m. weekdays.

Peak-hour use between 5 p.m. and 9 p.m. weekdays would be subject to a 5-cent a kilowatt hour premium.

"Mid-peak" users would pay a 2-cent per kilowatt hour premium during the hours of 7 a.m. to 5 p.m. weekdays. Other mid-peak and off-peak hours would be in effect on weekends.