CLIMATE SPECTATOR: Power prices and the carbon tax

With the carbon tax firmly in place, wholesale prices appear likely to stabilise at just a few dollars above the adjusted long-term average – assuming we have no more 'Yallourn-like' incidents.


Climate Spectator


With several weeks having passed since the introduction of the carbon tax, the place to look for the most immediate effect is in the national wholesale electricity market known as the NEM.

It’s early days yet, but NEM prices are certainly up. To what extent can we attribute the rises to the carbon tax? And will the sky fall in?

If we compare the NEM prices over the first two weeks of July with previous years we see a surprisingly large rise. For instance, in Victoria the early July 2012 prices were up by about $60 on the same time period for each of the previous three years.

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Volume weighted wholesale prices for Victoria for the first two weeks of July (in red) and first two weeks of June (in blue) by year. The plot on the right shows the difference (in green) between the July and June prices in a given year. The difference is typically less than ± $10, with the exception being the $50 difference this year. The question is how much of it is due to the carbon tax? Note that even though July 2012 prices are exceptional, they are still lower than in the winter of 2007. Data from AEMO, figure by Mike Sandiford

New South Wales and Queensland prices were also up, but not quite so much, at about $40 each.

With wholesale prices varying for a range of reasons, on timescales from the seasonal to the hourly, a better comparison maybe between time periods immediately pre- and post- carbon tax implementation.

Victorian prices in the first two weeks of July were up about $50 on the first two weeks in June in 2012. In both NSW and Queensland the price differential was about $35. In South Australia it was almost $60.

Given that about one tonne of CO2 is generated for about each megawatt-hour of coal-fired power, these price jumps are significantly more than expected for a $23 per tonne carbon price.
So what gives?

To work out what is going on, it’s useful to look at how average daily prices have changed over the last two months.

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Daily volume-weighted wholesale prices for Victoria for the two months mid-May to mid-July (red circles are weekdays, blue circles are weekends, circle sizes scale to total daily demand). Left panel shows absolute prices, right panel shows prices with the mean of June 6 to 30 subtracted. June 6 corresponds to the onset of Yallourn pit flooding due to failure of the Morwell River diversion. Data from AEMO, figure by Mike Sandiford

Up until June 6, daily prices averaged between $25 and $30 per megawatt-hour across the NEM. On June 6 prices jumped by around $10 across all NEM jurisdictions.

That price jump was largely due to the reduction in output at TRUenergy’s Yallourn power station following the Morwell River diversion collapse on June 6. The flooding in the open-cut mine and damage to the conveyor system that delivers coal to the power station caused power output to reduce by over one gigawatt.

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Yallourn power station output for the two months mid-May to mid-July spanning the Yallourn pit flooding due to failure of the Morwell River diversion on June 6. Data from AEMO, figure by Mike Sandiford

You might think the effect would have been largely limited to Victoria. However, interstate power flows allow the price signals of such outages to propagate right across the NEM. In fact, there was little difference in the price impact of the Yallourn outage between Victoria and the other mainland states connected to the NEM.

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Daily volume-weighted wholesale prices for NSW for the two months mid-May to mid-July. (Red circles are weekdays, blue circles are weekends, circle sizes scale to total demand). The plot on the left shows absolute prices, while the plot on the right shows prices with the mean of the period June 6 to 30 subtracted. Data from AEMO, figure by Mike Sandiford

If we factor out the price impact of Yallourn, we see the price hike in early July was initially about $35-40 per megawatt-hour. However, prices have dropped back considerably since the first week of July and are now only about $25 above late June prices. And the trend still appears to be heading downwards.

The initial carbon price hike at the beginning of July seems to have been a bit of an overshoot. Perhaps the generators were being somewhat ‘conservative’ in their bidding strategy in the brave new world of carbon pricing. If so, market forces appear to be quickly pulling them back into line.

If and when Yallourn comes back to full production, we could expect prices to drop back another $10 or so, and settle at around $50-$55 per megawatt hour. In a historical context, that's not much more than the $47 annual wholesale price averaged over the last 10 years when adjusted to 2012 dollar terms.

In the bigger picture, the overall impact of the carbon tax will have been significantly cushioned by the very low wholesale prices over the last few years. Those low prices reflect the general state of oversupply on the NEM as discussed in my last post.

In spite of the issues at Yallourn, and the impost of the carbon tax, wholesale prices have not yet reached the heights of the winter of 2007, and do not look like doing so. The sky didn’t fall in 2007 and won’t be doing so now. Unless of course we have another Yallourn-like incident on the NEM.

Wholesale prices are up, but the trend in prices since early July suggests they will stabilise at only a few dollars above the long-term average adjusted wholesale prices. And that is with the cost of the carbon tax.

Mike Sandiford is Director, Melbourne Energy Institute at the University of Melbourne.

This article was originally published by The Conversation. Republished with permission.

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