The option the authority is consulting on is expected to collectively save businesses and householders in Otago and Southland $64million annually.
While householders would save about $65 a year, the biggest winner by far would be the New Zealand Aluminium Smelters (NZAS) Tiwai Point facility south of Invercargill, which could save $56.3million annually.
The smelter employs about 800 people and supports up to 3000 jobs in Southland.
It uses 8% of all the electricity generated in New Zealand, most of that generated at the nearby Manapouri power station, but is charged 8% of total transmission line costs throughout the country.
Chief executive Gretta Stephens has consistently said internationally uncompetitive power costs, including high transmission charges, are affecting its profitability.
About 20 people attended the Invercargill workshop, including representatives from NZAS, Pioneer Generation, lines company PowerNet, economic development agency Venture Southland, and the Southland Regional Development Strategy Group (SoRDS).
Venture Southland chief executive Paul Casson described the workshop as "very good''.
"Everyone in the room fully endorsed what the authority is trying to do. The philosophy they are looking at is ideal''.
That philosophy rearranged the cost of maintaining and upgrading transmission lines to more clearly reflect the true cost of delivering transmission services.
Mr Casson said costs would decrease for consumers in 15 regions, including Otago and Southland, but increase in 14 others.
Southland would receive one of the largest benefits from the change, while the two regions losing out the most would be Northland and the West Coast.
Tiwai was a major contributor to the Southland economy and it was important it increased its profitability, he said.
"But a reduction in fixed costs would impact on other large business users too. We might be able to attract more businesses to Southland if electricity costs were lower.''
SoRDS governance board chairman Tom Campbell, a former general manager at Tiwai, said the workshop was "very useful'' and attendees welcomed the opportunity to ask questions and discuss options.
"There is no doubt the proposal is good for Southland and much fairer than the current system.''
The workshop was one of only four held during a consultation period that ends on July 26.
The other workshops were in Auckland, Wellington and Christchurch.
Mr Casson said there was still much work for the authority to do before a new pricing system was introduced.
"A decision is expected to be delivered in October, then [national grid owner] Transpower have until October next year to come up with an implementation plan to be in place by April 2019.''
