Yesterday, the Herald Sun ran an ostentatious double page spread under the tagline “Carbon Pain” as a prelude to Julia Gillard’s long-awaited tax announcement.

Next to an opinion piece by state energy minister Michael O’Brien sat an uncritical re-hash of a presser sent around by the Baillieu government on Wednesday examining the impact of a $25 a tonne carbon tax on Victorian battlers. According to the paper, the average “Melbourne residence with gas hot water” and the good old pizza shop were going to be slugged hard.

But it seems the figures underlying the government’s number crunching are dubious at best. Working backwards from the helpfully provided table (below), it can be rapidly deduced that O’Brien and the Hez back the assumption that generators will pass on the full $25 (now $23 according to reports), despite luminaries like Ross Garnaut suggesting otherwise.

Even more damning is the idea that, under a carbon tax, Victoria’s highly competitive electricity market wouldn’t reduce the amount of Co2 produced per megawatt hour by Victorian generators. O’Brien infers that generators would continue to emit between 1.1 and 1.17 tonnes of carbon dioxide per megawatt hour. Compare that with 0.4 tonnes of CO2 for gas-fired power and 0.8-0.9 for other coal sources.

The government reckons that with a carbon price of $25 per tonne, Victorians would end up paying an “extra $2.5 billion” to the feds, which is the same as Canberra yanking “$450 from the pocket of each Victorian.” The cost of electricity used by public hospitals and public transport would jump by “$27.7 million”.

Yesterday’s Herald Sun

The gas hot water household would see a “$129” increase in their annual power bill, while the pizza dude would be slugged with an extra “$550”. This is, of course, before the federal government’s generous compensation package is factored in that will probably leave most of those featured better off.

By sticking with the brown coal-fired status quo a suburban hairdresser might well expect an $825 jump in their power bill — but if, and only if, Victoria maintains its addiction to brown coal which currently produces 90% of the state’s power. Hazelwood, which produces up to 25%, is slated to be shut down completely and is currently asking the corporate regulator to overlook breaches in its license.

According to this informative document produced by the Australian Conservation Foundation and Environment Victoria in 2005, Hazelwood emits 1.6 tonnes of carbon dioxide per megawatt hour. It has actually increased its emissions intensity since 1998 and would rapidly turn to dust if the carbon price was ratcheted higher, as planned.

And in this paper published in March by ROAM Consulting, the economic impact on Victorians would be substantially less, perhaps $250 for a family using 7300 kilowatt hours per annum but only if the carbon price was increased to $30 a tonne.

Greens MLC Greg Barber slammed the assumptions underpinning the analysis this morning, telling Crikey that O’Brien’s table was a “primary school-level effort at economic modelling by abacus.”

He said it was built on the false assumption Victorian consumers would continue to choose dirty sources of power like Hazelwood.

“If you believe in the free market like me, the assumptions are totally unsustainable. You’d assume that with a carbon price in place other, less polluting, electricity generators will take market share off Hazelwood. That’s how the market works.”

The source for the modelling remains a mystery. O’Brien has said his “department” was involved, however interested parties are believed to be immediately seeking the working documents under Freedom of Information.

Baillieu government spinner Simon Troeth did not respond to a message left on his voicemail this morning.