Dubbed as the Iron Horse Energy Storage & Solar Project and located at the University of Arizona's Tech Park, the facility is E.ON’s first energy storage project in the continent. It comprises 10MW lithium titanium oxide storage facility and 2MW solar array.

E.ON’s energy storage facility provides frequency regulation and voltage control support to help Tucson Electric Power (TEP) in maintaining reliable electric service to its 400,000 plus customers.

E.ON Energy Storage North America VP Mark Frigo said: "Energy storage systems, like Iron Horse, allow utilities such as Tucson Electric Power to use renewable resources more effectively and efficiently within their electric grid. Energy storage has the potential to truly revolutionize the 21st century grid, and we are excited to be leading the way in this innovative new market segment."

The Iron Horse battery energy storage project broke ground in October 2016. Prior to that in July, E.ON signed a 10-year agreement with TEP to help the latter improve service reliability.

TEP Energy Supply and Renewable Energy senior director Carmine Tilghman said: "We expect energy storage systems like Iron Horse to play an increasingly important role in the delivery of safe, reliable electric service to customers as we continue our expansion of renewable resources.

"E.ON has provided our local electric grid with a cost-effective, reliable battery storage and solar system that will help us build a more resilient grid for our customers."

According to E.ON, the lessons learned from the Iron Horse project are applied to its Texas Waves projects which are being constructed and expected to be commissioned by the year end.