The final portion of the largest solar panel installation in North America is expected to be brought online this month, saving Nellis Air Force Base $1 million a year.

The 15-megawatt, 70,000 solar-panel array covers 140 acres of the base, located outside of Las Vegas. The solar panels are set up so they can follow the sun throughout the day.

When fully utilized, the installation is expected to provide up to 30 percent of the base's power and save about $83,000 a month in energy costs.

The project, started in June this year, is a collaboration between Nellis Air Force Base, solar panel manufacturer SunPower Corp., financers and government.

The panels, constructed by SunPower, are owned and operated by financer MMA Renewables, and the base will purchase electricity generated from the panels at a fixed rate, according to a USA Today report. Investors will cover the project's expected cost of $100 million and utilize federal tax subsidies for solar power.