Hawaiian Electric Co. wants to offer a discount to encourage electric vehicle owners to charge their cars overnight when power consumption is down.

The initiative would offer lower electric rates during off peak hours between 9 p.m. and 7 a.m., according to a release from HECO.

On Oahu the proposed rate would be about 6 cents per kilowatt hour below the residential rate. Under the plan, HECO would increase rates for charging electric cars during peak hours between 5 p.m. and 9 p.m. That rate would be about 3 cents per kilowatt hour above the residential rate.

Neighbor island residential off-peak charging rates will be about 7 to 10 cents per kilowatt hour lower than the residential rate.

The proposed three-year pilot program will be open to 1,000 customers on Oahu, 300 in Maui County and 300 on the Big Island for charging highway-capable electric vehicles. The pilot project rates would go into effect Oct. 1 for three years, pending approval by the state Public Utilities Commission.

"Our goal is to make Hawaii EV-ready as new, highway-capable EVs are expected to hit the market in the coming year," said Robbie Alm, Hawaiian Electric executive vice president.

"We also want to send a message to automobile manufacturers to include Hawaii among the first markets where EVs are available. This is another step in our commitment to the Hawaii Clean Energy Initiative."

The Blue Planet Foundation, a local nonprofit working to accelerate Hawaii’s transition to clean energy, said it supports the proposal.

"Blue Planet applauds Hawaiian Electric’s move to make electric vehicles more cost effective while taking advantage of off-peak power," said Jeff Mikulina, Blue Planet executive director. "Because an increasing amount of off-peak power is from renewable sources, this proposal would put more clean energy into the ‘gas tanks’ of Hawaii’s vehicles."

The proposed rates could provide a substantial savings for motorists, HECO said in the release.

For example, on Oahu a midsize internal combustion engine sedan with average fuel economy of 27 miles per gallon has a fuel cost of 12 cents per mile at $3.35 per gallon of gasoline. At current electricity rates on Oahu, including the discount for the off-peak rate, a midsize electric vehicle with a range of 100 miles on a 24-kilowatt battery has a charging cost of 5 cents per mile. The July residential electricity rate is 25 cents per kilowatt hour, or 19 cents per kilowatt hour with the discount.