The solar array will be capable of generating more than a million kilowatts per year and will help power the plant's new ultraviolet disinfection equipment.
Bernie Schroeder is the city's public works director. She says ratepayers will ultimately see some savings.
"The savings is in the fact that with the construction of the solar project, it offset the higher power consumption for the UV system. So it allows us to keep the rates where they are."
Schroeder says, depending on how much sunlight the city gets, the new system will generate up to 95% of the plant's electricity needs.
The facility serves more than 5,000 homes.