The Greens were told that a ban on new coal mines for three years would cost $3 million, while an indefinite ban would see a loss of $271m to $441m, including $71m in lost royalties and revenue from the Energy Resource Levy.
There were no costs for a three-year moratorium for new drilling and new fracking consents, as existing production would continue. But an indefinite ban on new drilling would see a loss of $6.2 billion, while a ban on new fracking consents would cost $8.8b.
That would mean an indefinite moratorium on all three would total over $15b - likely much more as production from potential new discoveries were not included, nor were indirect costs such as the adverse impacts on business confidence and security of energy supply.
"We have not attempted to cost indirect effects such as impact on business confidence in the sector, security of energy supply, or fuel substitution - however we expect there would be material impacts," said the papers, prepared by officials and released by the State Services Commission.
The ban on fracking included sites that had permits but had not started drilling. It noted that a three-year moratorium on fracking could open the Crown up to compensation claims from companies that had spent $1.14b to develop fields for fracking.
Data was not available to calculate future job losses - but officials estimated coal mining jobs to be in the thousands.
The Greens did not gain any mining moratoriums in its confidence and supply agreement with Labour, but won broader climate change policies including the introduction of a Zero Carbon Act and setting up an independent Climate Commission.
Conservation Minister Eugenie Sage has indicated that she wants to ban all new mining on conservation land, which raised concerns from the mining industry about job losses in regional New Zealand.
Directly after the negotiations, Prime Minister Jacinda Ardern said New Zealand's future was not in fossil fuels and she will review the annual Block Offer for petroleum exploration.
"Those Block Offers and their popularity have diminished over time. It's become less economic, particularly for offshore," she told The Nation in October.
"It's not where our future lies, but my plan is to transition our regions, not to jar them."
One welfare change the Government has signalled it will do is removing the sanction for a solo parent to name the other parent, usually the father.
Officials told the Greens that doing so would likely reduce the number of beneficiaries who name the father, which then obliges them to make child support payments that total about $185m a year.
The Greens asked about the costs of increasing core benefits by 10 per cent ($467m for the 2019/20 year) and by 20 per cent ($893m for the 2019/20 year), and removing excessive sanctions and financial penalties for those on welfare ($34m a year).
"The removal of employment obligations and services would also be likely to reduce the number of beneficiaries exiting to employment," officials said in the papers.
In its agreement with Labour, the parties agreed to a non-specific overhaul of the welfare system and removing "excessive sanctions".
Transport officials told Labour the cost of connecting Northport to Auckland by rail would cost up to $3.5 billion and if not commercially viable, there would be "significant" ongoing costs for KiwiRail.
The coalition agreement between NZ First and Labour provides for the $1 billion a year regional development fund to be used to fund a feasibility study on options for moving the Ports of Auckland – "including giving Northport serious consideration." The fund will fall well short of what was needed to fund the Northport proposal itself if officials' costings are correct.
In August Peters rejected KiwiRail estimates that upgrading Northland's rail to carry freight and adding a new 18km line to Northport from Oakleigh would cost up to $1 billion while a further $2-3 billion would have to be spent on upgrading the line from Swanson through to Auckland.
Labour requested the latest estimates during the negotiations and the Ministry of Transport responded while it was yet to be fully costed, creating the new line from Oakleigh to Northport would cost $200 million, upgrading the line from Oakleigh to Swanson $100 million and upgrading the line from Swanson through to Auckland $2-3 billion.
The officials noted that no business case of assessment of commercial viability had been done: "there is uncertainty about the extent to which any rail extension would be commercially viable. Should the investment prove not to be commercially viable, then there would be significant ongoing operational cost for KiwiRail."
National's transport spokeswoman Judith Collins said it was a huge amount of money and bucked Peters' claim during the election that it could be done for about $250 million.
"It shows when Mr Peters was talking about $250 million he must have been thinking about another century. You're looking at almost four years of Shane Jones' provincial growth fund. It's that sort of thing that means other projects just don't get built."
The cost of the new line included land purchases, junctions and a rail yard. The upgrade for Oakleigh to Swanson would require creating larger clearance through tunnels, replacing 18km of light weight rail, replacing some bridges, strengthening some sections of the rail, and upgrading the radio communications system.
It said there was a possible second option which would allow for a lesser upgrade of the existing line, but would require bespoke rolling stock and staff expertise. That had not been costed.
