A backup power plant at Daniel K. Inouye International Airport is now in full operation nearly five years later than originally expected.

Always Investigating previously reported that the multimillion-dollar, 10-megawatt standalone generation project was supposed to open by the fall of 2012 to keep the airport running in the event of an island-wide blackout.

But, as Always Investigating uncovered, the system remained stuck in a testing loop, unable to automatically kick into gear. The state kept changing its mind about what exactly it needed built, the contractor got paid for wait-around time, tech and specs changed as the years went on.

“In this particular case, the changes had to do in what we asked for,” Department of Transportation director Ford Fuchigami previously told Always Investigating. “We found going through the testing there were some difficulties. We have to make sure this thing is functional, is what it is. We don’t want to put this thing online just for the sake of putting it online because of the fact we made a deadline. This has to work.”

The state Department of Transportation now tells us final testing of the facility was completed earlier this month, and the plant began providing electricity to the grid last weekend.

The state-owned Emergency Power Facility (EPF) uses four generators running on biofuels to provide up to 10 megawatts of power. During non-emergencies, the EPF is operated by Hawaiian Electric to provide electricity to the grid. In an emergency, it can be operated in “islanded” mode to provide backup power for the airport.

The plant was designed to withstand a Category 5 hurricane and a 2,500-year recurrence earthquake. It can also use jet fuel in a protracted emergency.

Hawaiian Electric pays the Airports Division for its use, and also pays for the maintenance of the generators.

“This is a great example of a public-private partnership that provides benefits to our community and to the tourism industry,” said Ron Cox, senior vice president of operations for Hawaiian Electric. “These new, efficient generators are a cost-effective addition to the resources available to meet the island’s energy needs.”

The project was initially budgeted at $20 million, but wound up costing the state $23 million.