The Amadeus ruling is likely to help feed into the regulatory environment around the North East Gas Interconnector, as that proposed $800 million pipeline to be owned by Asian conglomerate Jemena will hook into the Amadeus gas pipeline at Tennant Creek.

First NEGI gas is predicted in 2018.

The Amadeus gas pipeline is a vital link between the three Amadeus Basin oil and gas fields owned by Santos and Central Petroleum and their markets in the Northern Territory, and will be a key transit path for gas from Eni's Blacktip field, in the offshore Bonaparte Basin to support NEGI's foundation customer, Incitec Pivot in Queensland.

Its draft decision allows APT to recover $110.7 million over five years between 2016 and 2021, 21.1% less revenue than APT's proposal.

It sets the allowed rate of return at 6.02% for 2016, below the proposed 8.3% because the investment environment has improved since the previous decision in 2011.

AER chairwoman Paula Conboy said the draft decision provides for reductions in revenues below those proposed by owner APT Pipelines.

"The AER's draft decision reflects an improved investment environment with significantly lower interest rates compared to previous years, which translates to lower financing costs necessary to attract efficient investment," she said.

The regulator is now seeking views from APT and other stakeholders, and will hand down its final decision in April next year.

Separately, the AER has issued a draft decision and outlines several key changes to Australian Gas Networks' South Australian access proposal.

AER suggested a tariff reduction of 23% before inflation on 1 July 2016, up from the 11% reduction proposed by AGN; a reduced rate of return of 6.02%, down from AGN's suggested 7.23%, a 4% reduction in proposed operating expenditure; and a 43% reduction in proposed capital works, which is primarily driven by a significant reduction in the volume of mains replacement to be undertaken.

Conboy said the AER's draft decision provides for reductions in revenues below those proposed by AGN because of a lower rate of return and reductions in forecast capital expenditure.

"The AER's role is to ensure that consumers pay no more than necessary for the safe and reliable delivery of gas by approving the overall revenue that is used to set AGN's network charges," she said.

"This means allowing sufficient revenue for AGN to maintain its existing network, and to meet new growth and augment the network where necessary."

The AER's draft decision reflects an improved investment environment with significantly lower interest rates compared to previous years, which translates to lower financing costs necessary to attract efficient investment, she said.

The AER is now seeking feedback from AGN and other stakeholders. The AER will consider AGN's revised proposal and all stakeholder views before making its final decision April 2016.

"The AER's draft decision supports gas as a low cost, low carbon energy source for South Australians," AGN CEO Ben Wilson said.

"AGN does have concerns with certain aspects of the AER draft decision, including cuts to our proposed mains replacement program.

"We will provide the required additional information to the AER so that the final decision better promotes the long term interests of gas customers and the general public."

AGN and other stakeholders have until January 6, 2016 to provide responses to the AER's draft.

The regulator is also seeking input on access arrangements for ActewAGL distribution's gas network from mid-2016.

As with AGN's pipeline, the decision on the Australian Capital Territory and south-east New South Wales' utilities access agreements is because of a lower rate of return and reductions in forecast capital expenditure.

"This means allowing sufficient revenue for ActewAGL to maintain its existing network, and to meet new growth and augment the network where necessary," Conboy said.

The AER's draft decision reflects an improved investment environment with significantly lower interest rates compared to previous years, which translates to lower financing costs necessary to attract efficient investment.

Decisions will be made in April for all three access agreements.