Like most big infrastructure projects - including Snowy Hydro itself - cost blow-outs seem inevitable. Risks and complications are either not imagined or ignored. Worse, it is usually someone else who carries the cost. In the case of overhead powerlines, it is farmers, bushfire victims, and the taxpayer generally.

Economists call these "externalities". It's a nice little earner for miners, industrialists, and manufacturers if they do not have to pay for injured workers, pollution, lost tourism, fire risk and so on. When you add the externalities, many of these projects would not go ahead, or be less profitable.

An extreme example is asbestos. Australia would have been better off if not one gram of it had ever been mined, even if a mining company or two and their shareholders scooped up fat profits.

Snowy Hydro has been a costly fiasco - now six times the original cost. Surely, it does not have to be made worse by overhead transmission. The case for going underground and even for government subsidies is compelling.

Transgrid estimates the overhead cost at $3.3 billion and the underground cost at $11.5 billion.

Others say the $3.3 billion is an under-estimation and the $11.5 billion is an over-estimation. Transgrid, of course, wants to maximise its profits by minimising its costs. Transgrid is 35 per cent Australian-owned and the rest is owned by Canadian and Middle Eastern interests.

Transgrid says: "The cost of undergrounding ... is unsustainable as the additional cost will be passed on to commercial, industrial and private electricity consumers, at a time of great concern about escalating electricity prices."

But a report out this month by Australian engineering consultancy Amplitude says could be put underground for $5.5 billion.

When you look at the vast risk and inevitable extra cost of overhead powerlines, the extra $2.2 billion would be money well-spent.

Judging by past events, the bushfire risk is obvious. Five of the 11 major fires of Victoria's 2009 Black Saturday, which killed 173 people, injured 414 people, and burned through 450,000 hectares, were caused by powerline sparking.

They were to blame for the 2013 Blue Mountains bushfires that destroyed 196 homes. The list goes on. And whatever the cause of a fire, powerlines are a menace when it comes to fighting them. Fire debris and smoke result in more dangerous arcing.

Fire and resulting greenhouse gas emissions caused by overhead powerlines jeopardises the whole purposes of Snowy Hydro 2.0.

There is a good case for government to step in, but Australian governments have a poor record when it comes to stopping large corporations from doing exploitative things and passing the costs on to everyone else. For example, Australia raised only $2.4 billion from the Resources Rent tax last year, whereas Norway raised nearly $90 billion in taxes from its oil and gas industry.

The Australian government should take a much closer look at the whole Rewiring the Nation plan.

Fires are not the only cost of overhead powerlines. Overhead lines result in more outages than underground lines. They are susceptible to falling branches, high winds and lightning strikes that underground cables avoid. They disrupt wildlife, destroy wildlife habitat and do great damage to farms.

They require wide cleared strips of land for long-term and constant maintenance. They are a hazard to birds and aircraft. They produce a wide hazardous electromagnetic field.

There is also a political risk. They will add to the rural-urban divide and rural resentment. The 2022 election and the Voice referendum revealed that growing divide and a feeling in rural areas, whether justified or not, that the government helps elites in cities at the cost of regional areas.

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The Coalition is exploiting the feeling among rural Australians that they suffer from ugly powerlines and wind and solar farms to satisfy climate change targets set by city dwellers and to satisfy the electricity demands of higher city populations driven by higher immigration.

The new Coalition policy is not to deny climate change, but to blame Labor for any inconvenience in doing anything about it. It is as if the Liberal Party has given up on winning back the Teal seats and is concentrating on Labor seats outside city centres.

Exploiting resentment is easy politics. As are uncosted, unrealistic suggestions that coal-fired power stations could be replaced by small nuclear power stations using the existing grid. It seems like a good idea, but does not stand up to close analysis.

In Germany in 2015, Angela Merkel's conservative government began a program of replacing overhead wires and committed to putting all new wires underground. In Germany, 73 per cent of the medium voltage cables are underground and 87 per cent of low voltage cables are underground.

Yes, there are disadvantages to underground cabling, particularly the initial cost of more expensive insulated cable and higher capacity cable for future-proofing. But what looks cheaper and easier in the short-term carries significant longer-term costs.

Some of those costs cannot be quantified because the cost of bushfires started by overhead powerlines cannot be predicted and you cannot put a price tag on aesthetic beauty.

Overall, the transfer to renewables will cost and will disfigure. Windfarms and solar farms, of their nature, cannot go underground, but with new powerlines, where there is a less disfiguring and not much more costly option, we should take it. Indeed, power supply would be more secure if existing overhead lines were progressively put underground.

In any event, we should certainly not accept the cost-benefit analysis of large corporations who will profit from the projects they are proposing while shifting as much of the cost as possible to the community at large.