A single council for the Bay could save up to $10m a year but the move to merge Wairoa, Napier, Hastings, CHB and Hawke's Bay regional councils could cost $18.4m.
The proposal, by A Better Hawke's Bay, would also mean up to 100 public servant jobs will be cut if the five councils were merged.
The figures were released in the second and final part of the Hawke's Bay region Prosperity Study by consultants McGredy Winder & Co. The report was tasked to refine cost and saving estimates associated with local government reform options, after the scrutiny of figures identified in the first report released in August 2012.
The report reviewed three scenarios including the A Better Hawke's Bay plan for a single council, a second scenario for a single territorial council and the existing regional council and a third for two territorial councils north and south of the region as well as the existing regional council.
The report said between 90 and 100 jobs would be reduced under the A Better Hawke's Bay Plan. The second scenario would involve jobs cuts of between 70 and 80 while the third, 30 to 40 jobs.