A key problem causing Hawaiian Electric Co. to ask customers to cut down on evening electricity use should be resolved in two to three days, the company said Wednesday.

The utility sent out two notices in the past nine days asking its Oahu customers to conserve energy use between 5 and 9 p.m. to avoid power outages.

The utility said an out-of-service power plant at Kalaeloa was a major reason for the call for energy conservation. The oil-fired Kalaeloa plant has a leak in one of its boilers, which will take two or three days to repair, HECO said.

That should restore about half of the plant’s generating capacity, said Darren Pai, Hawaiian Electric spokesman. A separate problem with the plant’s connection to the electric grid must be fixed before it can return to full power. That will take up to two weeks to repair, Pai said.

HECO has enough power without the Kalaeloa plant to get through the peak evening hours, but the margin of error is thin.

"If another generating unit develops an unexpected problem and goes out of service, there may not enough generation to meet demand," Pai said in an email. "In this situation, power outages may occur."

The Kalaeloa plant, located in Campbell Industrial Park, experienced problems before HECO’s initial call for conservation on Sept. 8.

That notice to customers was the first time the utility had to ask the community to decrease energy consumption this year, Pai said. High electricity demand due to hot weather and little power being provided by the two North Shore wind farms were additional contributing factors to the utility’s problem supporting energy demand in Oahu.

The calls for conservation show the changing role of the customer in energy management, said Jeff Mikulina, executive director of Blue Planet Foundation, a nonprofit clean energy organization.

"We’re going to have a future energy system where customers are more participatory, where they are a part of the solution, " Mikulina said. "We envision the system of tomorrow being one where you help in participating by shifting the loads and balancing that load with the supply."

Among HECO’s 300,000 Oahu customers, 34,000 residential customers and about 70 commercial customers have joined in a voluntary demand response program. HECO, for example, can remotely shut off the hot water heaters of participating customers to reduce demand. The utility has used the program over the past eight days, Pai said.

"Our system operators have used our demand response programs to help manage the demand for power during the evening peak," Pai said. "Demand response helps manage the demand for electricity by reducing the energy output of certain appliances or equipment, such as water heaters for participating residential customers and non-essential lighting and heating or cooling systems for participating commercial customers."

Mikulina said energy storage — the use of batteries connected to renewable sources — will help solve consumption problems in the future.

"I think those entrepreneurial solutions like that would solve (the current) problem," said Mikulina. "What we saw yesterday and eight days ago shows kind of how fragile our system is. We need diverse energy built around a modern smart grid."

HECO is asking that customers continue to cut back on energy use during peak evening hours over the next several days as repairs for the Kalaeloa plant are addressed.

The Kalaeloa plant, owned by Kalaeloa Partners, is the largest independent power producer on Oahu. The plant accounts for about 12 percent of the total energy from HECO’s nonrenewable, or firm, energy sources, such as oil and coal.

Kalaeloa Partners is owned by Newark, N.J.-based Public Service Enterprise Group and Birmingham, Ala.-based Harbert Power Corp. They acquired the plant in 1997.

Kalaeloa Partners did not return calls Wednesday seeking comment on the outage.

Pai said the repairs to the Kalaeloa plant’s grid connection are complicated.

"These types of repairs are time consuming because they must be done very meticulously to ensure safety of the crews and to preserve the integrity of the high voltage cables,"said Pai. "If done improperly, the cables may be damaged and the repairs will need to start over. In addition, Kalaeloa needs to bring in parts from the mainland to complete those repairs."