Hawaiian Electric Co. said it began deactivating its downtown power plant today, nearly a century after the generating station first started providing electricity.

“Thanks to the tremendous growth in renewable energy and more efficient use of electricity by our customers, we’re able to deactivate older, oil-fired generating units,” said Ron Cox, Hawaiian Electric’s vice president of power supply.

 The plant’s history dates back to 1920 when the site at Halekauwila and Alakea Streets was first constructed, the company said. Its location was particularly meaningful, as it sits at the harbor where whaling vessels once off-loaded the oil that was used to power the city’s lamps.

“The full deactivation process will take several months. The plant’s two generating units must be cleaned and the equipment must be preserved to protect it from corrosion. The careful and deliberate process and appropriate preparation ensures the two units can be reactivated during emergency situations,” the company said.

“By contrast, ‘retirement’ or ‘decommission’ means a generating unit is permanently removed from service and no longer available for use under any circumstances.”