(BIVN) – More rolling power outages, as early as Monday morning, will be possible on Hawaiʻi island due to a continued generation shortfall, and “lower than normal wind and solar resources.” 

Hawaiian Electric and the Hawaiʻi County Civil Defense issued another alert on Monday morning, following a night of power outages for many island residents. 

The utility says 21,557 customers around the Big Island experienced a 30-minute outage last night, starting at 8:54 p.m. and ending at 9:59 p.m. 

After the Sunday evening outages were over, Hawaiian Electric asked customers to conserve electricity use and posted this explanation:

The request for conservation is prompted by the unavailability of several large generators. Hawaiian Electric’s Hill 5 steam unit tripped offline yesterday. Its Puna steam unit and CT-1 combustion turbine unit also are under repair. Its Keahole CT-5 unit is expected to return from annual overhaul by the end of April. These units generate about 62 megawatts combined. In addition, independent power producer Hamakua Energy is offline. The island’s largest generator provides up to 60 megawatts to the grid. In addition, wind and solar resources are forecast to be lower than normal.

Last month, Hawaiian Electric urged residential and business customers to conserve energy through the end of April due to the unavailability of several large generators. Conservation helps ensure that enough power is available for all customers, especially between 5 to 9 p.m. when electricity use is highest.

The impacted areas and the timing of the outages are based on the amount of electric demand that needs to be reduced, the utility says.