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status: [25th Jan 2012]: Round 3 data.

Electricity Price Data

Introduction

Electricity price data for the National Electricity Market (NEM) states, 1999 to 2011 inclusive.

The price is the wholesale Regional Reference Price in dollars per MWh. Each NEM state is a region, and the market prices electricity in 30 min time chunks. Note that prior to mid-2008 the SNOWY region was considered separately.

The data presented here is the AEMO "price_demand" data, repackaged from 700+ csv files into a single price flatfile, and alternatively as basic yearly CSV files. [more details]

This data page is one of three closely connected pages: (this) Price Data page, the Electricity Demand Data page and the Price, Demand and Value - Electricity Market Analysis page.

The raw data

Here is the data in 'day-per-line' OzEA format:

• Price at 30min intervals (2.8 MB gziped flat file; i.e. unzip and view in a basic text editor)
• log file - details misisng data (2 KB text file)

Note that the small number of missing data points are mostly common across the regions.

Also, here are some basic CSV files containing the thirty minute data for the NEM states for each of the years: 2009, 2010, and 2011 (can provide other years in this format if requested).

Some characterisation

First, here are some price histograms. Note that while the wholesale electricity price is mostly around $10-50 MWh, it sometimes reaches the imposed market cap (now $12,500 MWh, was $10,000 MWh). And sometimes the price can go negative (i.e. a generator that cannot switch off must pay to use the grid as a 'dump' load). The linked histograms show only the ~ 0-100 range. Note various structures coming through (e.g. SA 2011, TAS 2009), which can not be 'noise', and are supposed to be artefact of market operation. Please comment if you can expound on these structures.

As an overview of all the price data, we plot the median price for each month for each region. Of course we are not equating 'price', with 'median monthly price' - and neither should you! This is simply a nice way to get a overall view (click image for a pdf).

Two points are of particular note: first, the introduction into the NEM of Tasmania in 2005 clearly involved some transients; the 2007 peak was related to a lack of water, in particular restrictions on the use of water in electricity generation (cooling in coal plants) in Queensland.

Here is a corresponding plot showing the 'mean monthly price', with a caution that the use of means is problematic when data is highly skewed, as it is here. More on the tail into high spot-prices shortly.

The following plots show how often the wholesale electricity price was above a given value (e.g. 10⁰ on the y-axis is the 1% line; 10² on the x-axis is the $100 MWh line), for the given year.

We observe in the above plots that, overall, the percentage of the time that the price is at elevated levels has been receding (maybe not so much for NSW). Here are some tabulated price-points, corresponding to the above plots, giving the percentage of the time that the price is in the given ranges:

      2011                               2010                              2009
        <$1   <$10    >$100  >$1000        <$1   <$10   >$100  >$1000        <$1   <$10    >$100  >$1000
------------------------------------     -----------------------------     -------------------------------
SA      0.79   2.2     0.6    0.13         0.83   3.2    0.9    0.25         0.65   3.0     1.9    0.43
TAS     1.00   2.6     0.4    0.01         0.46   2.6    0.6    0.12         1.26   4.8     3.6    0.37
VIC     0.11   1.9     0.3    0.05         0.07   1.9    0.6    0.22         0.18   1.6     1.1    0.15
NSW     0.01   0.03    1.1    0.17         0.05   0.4    0.5    0.15         0.03   0.5     1.7    0.32
QLD     0.09   0.4     1.1    0.13         0.21   2.1    3.2    0.11         0.03   0.7     1.5    0.19

Comments

The above characterisation work is presented without significant comment, for now at least. The commenting facility below provides a mechanism for any discussion, or further characterisation work, you may have to contribute.

The price data goes hand in hand with the demand data, and these are examined in combination on the Electricity Market Analysis, Price, Demand and Value page (the principal follow on point from this page).

3 OzEA_DEPD0003

francis Subject: daily price cycle Date: 2010-11-18 (at 02:40:50)

With the wholesale electricity market priced every 30 mins, there can be opportunities to make money with 'buy low and sell high' strategies. The most pure of these is some form of storage, although displacement is the same in terms of the effect on demand. To get a starting foothold into the price variability, here we look at the daily cycle of minima and maxima. Specifically:

- take the SA 2009 wholesale electricity price data
- find the maximum price each day
- find the intervening minima
- construct differences (from the low to the next high)
- plot:



Note that all values greater that $200 MWh (up to 10,000) have been drawn down to 200. We see that the value of storage / displacement, on a daily cycle, is around $30 MWh.

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fc - Jan 2012