With two major generators unexpectedly offline, Hawaiian Electric asked Oahu customers to conserve electricity Monday between 5 p.m. and 9 p.m. to avoid the possibility of power outages.

Officials issued the call Monday as hot and muggy weather continues to drive up air conditioning use and demand.

In addition, two major generators — one operated by independent power producer, Kalaeloa Partners, and one at Hawaiian Electric’s Waiau power plant — are unavailable. 

As a precaution and to ensure sufficient power is available to meet the early evening peak demand for electricity, Hawaiian Electric is asking residential customers to conserve energy.

The time between 5 p.m. to 9 p.m., they said, is especially critical because customer usage normally climbs due to early evening cooking, bathing and other activities.

Kalaeloa Partners normally provides 208 megawatts of generation to support the island’s energy needs. The plant went out of service unexpectedly Sunday evening and has since restored about half of its output. The cause of the plant’s initial problems is still under investigation by Kalaeloa Partners with assistance from Hawaiian Electric, officials said.

In addition, a 90 megawatt generator at Hawaiian Electric’s Waiau power plant experienced problems earlier and will not be back online until later Monday evening.

Other resources such as wind farms are normally able to assist in meeting evening electricity needs, however, they are not projected to do so tonight due to the light winds across the island, officials said. 

Although Hawaiian Electric anticipates it will be able to serve the evening peak demand for electricity, available backup generation reserves will be very low. Should demand for electricity remain high and another unplanned loss of generation occurs, power outages may occur, they said.

The power company is also asking its larger commercial customers to voluntarily reduce electricity usage.

For residential customers, suggested steps include  turning off or lessening use of air conditioners, delaying hot showers and dishwashing activities and minimizing cooking until later in the evening.

"We appreciate everyone’s understanding and cooperation. We understand the evening hours are an especially inconvenient time to cut back on electricity, but with everyone’s help we can avoid an emergency situation," said Darren Pai, Hawaiian Electric spokesperson.