It is now three weeks and three days since the Climate Change Commission extended the submissions deadline for its draft emissions budgets by two weeks.

The extension was prompted by concerns about the Commission’s refusal to release selected data from its models.

The extension pushed the submissions deadline just beyond four weeks, the required turnaround time under the Official Information Act (OIA). We immediately lodged an OIA request with the Commission for “all data on the marginal abatement costs of electric vehicles”. The Commission’s response is due in five days.

Our request aims to solve an enduring mystery behind the centrepiece of the Commission’s emissions strategy, their proposed ban of petrol and diesel light vehicle imports from 2032. Under the Commission’s plan, only electric vehicles (EVs) will be imported after that date.

The question is how the Commission’s models, which optimise for least cost reductions in emissions, could have arrived at a strategy to go hard and early on EVs. EVs are currently expensive relative to conventional vehicles. The Commission’s analysis implies EVs will only become competitive in their own right in the late 2030s. Research suggests that, for now, EVs are among the least affordable ways to reduce emissions.

On its face, the better strategy is to reduce emissions via other channels first and shift to EVs as costs come down.

So far, the Commission has refused to release all of its assumptions. It has not given a plausible explanation. Speaking to Parliament’s Environment Committee on 25 February, the Commission’s Chair and Chief Executive implied the data had already been released or does not exist. But is this actually the case?

It is conceivable the Commission has used negative costs in its models to prop up its EV strategy. In 2018, a study by the Ministry of Transport (MoT) found the Feebate policy, an EV subsidy, reduces emissions at a negative cost. MoT counted all of the benefits of EV ownership, mostly fuel savings, but appears to have counted only some of the costs.

If this is the case, then the Commission’s EV strategy, one of the more draconian policies ever seen in this country, might not survive five minutes of scrutiny.

Transparency is essential. As the Chair of the Major Electricity Users Group said, “If the modelling is robust enough for the Commission to use to make far-reaching recommendations, it should be robust enough for scrutiny.”