A new $2 million solar photovoltaic array serves as shade over about 150 parking spaces at the headquarters of National Bank of Arizona, on Wilmot Road. The installation will produce power for the bank and its tenants. GREG BRYAN / ARIZONA DAILY STAR

National Bank of Arizona will throw the switch on a 402-kilowatt, $2 million solar photovoltaic array at its Southern Arizona headquarters today.

The 24,000-square-foot solar installation will shade about 150 parking spaces on the roof of the parking garage adjacent to the bank headquarters at 335 N. Wilmot Road.

The array - one of Tucson's largest - will produce about 580,000 kilowatt-hours of electricity for the bank and its tenants in two office buildings on North Wilmot Road. That equals the average annual consumption of about 55 homes in Tucson - enough to supply 25 percent of the buildings' needs.

Figuring in renewable-energy-credit payments from Tucson Electric Power Co. and a 30 percent tax credit from the U.S. government, the bank will be able to recoup the cost of the installation in six years through reduced electric bills, said Dave Lyons, Southern Arizona regional president for the bank.

Lyons said the 200 employees of the bank are excited about "having a greener footprint."

National Bank of Arizona CEO Keith Maio, Mayor Bob Walkup and U.S. Rep. Gabrielle Giffords planned to attend a dedication event today, ceremonially switching on the solar array.

The bank, a division of Zions Bancorporation, installed a 222-kilowatt solar system on its Phoenix headquarters in May 2009. It has financed more than $100 million in solar projects, including the Soaring Heights residential community at Davis-Monthan Air Force Base, said Craig Robb, managing director of Zions Energy Link.

Contact reporter Tom Beal at tbeal@azstarnet.com or 573-4158.