The Auckland Transition Agency says further savings of up to $100 million per year could flow from the amalgamation of the eight councils in Auckland into the new super city.
The agency, which oversaw the merger, says economists see potential savings of between $175 - $195 million within six years.
The savings equate to 10% of revenue in rates.
The Transition Agency says the amalgamation process has saved $37 million this year, after transition costs.
Rates rises forecast to start from next June have been lowered from an average 6% to 3.9%.
The new Auckland Council comes into being on 1 November. It will decide the final figure and whether savings will mean lower rates or enable new spending.