The system comprises a 1MW array, which covers one hectare of water surface and consists of more than 2,700 solar panels
The electricity will be used for pumping and aeration for the natural bacteria that break down the waste as part of the treatment process.
The project, which will generate enough power to run the equivalent of 200 homes for a year, is forecast to reduce carbon dioxide emissions by 145 tonnes annually.
The array is the latest in a series of five solar projects and is expected to help the company meet its costs savings and emissions reductions targets.
Auckland Mayor Phil Goff said: “Large solar installations like this are common overseas and it’s good to see we are now making use of the technology in New Zealand.”
Watercare Chief Executive Raveen Jaduram commented: “Most of the wastewater is moved around the plant by gravity and almost all of the energy comes from biogas, a byproduct of the wastewater treatment process. The array will contribute to our long-term goal of being energy-neutral at the plant.”