There’s more public parking — and more renewable energy — at Daniel K. Inouye International Airport after the installation of 4,260 solar photovoltaic panels at the Terminal 1 parking garage was completed Friday.

The work began Aug. 20, and now done, the state Department of Transportation was able to reopen 346 parking stalls on the seventh level of the garage, where the panels also are providing shade for parked vehicles.

The solar energy generated by the system will be used throughout the airport, and when combined with other conservation measures will reduce the facility’s electric bill by nearly half, according to DOT.

Installation of nearly 3,000 more solar panels will start in January on the fifth level of the Terminal 2 parking garage (formerly the overseas terminal).

DOT said its $207 million contract with Johnson Controls Inc. for various energy-saving improvements at Hawaii airports is being financed from guaranteed energy savings, not taxpayer funding.

The projects, which began in 2014, include replacing 98,000 light fixtures with high-efficiency, light-emitting diode technology and energy-efficient lighting, upgrading ventilation and air-­conditioning systems and installing more than 24,000 solar photovoltaic panels.

DOT said it expects more than $600 million in guaranteed cost savings over the 20-year life of the contract.