Clarifying Notes about the Data

NEM Time

First things first - it is essential to understand that the NEM is operated on Australian Eastern Standard time (GMT + 10 hours) - which means no daylight savings. All data published by AEMO (and hence updated by NEM-Review) is stamped on this basis.

NEM Time Intervals

It is important that you are aware that, in real-time, the NEM operates in two different intervals:

Dispatch (5-minute) Intervals

AEMO dispatches the market on a five-minute basis.

In doing so, AEMO takes generator's bids to supply, and assumes what the demand in each region will be at the end of the current five-minute (dispatch) interval to determine:

  • what each generator should be producing at the end of the five minute interval, and hence
  • the dispatch price.

It should be understood that the dispatch data is data derived from the dispatch algorithm for the end of each dispatch interval. Specifically in terms of generator production, regional demand, and interconnector flow:

  • the data is an instantaneous value (i.e. MW rather than MWh); and
  • the data is not actual metered data, but rather derived from calculations.

Trading (30-minute) Intervals

Even though the dispatch process is operated on a 5-minute basis, commercially the NEM operates on a half-hour (trading) basis.

The trading interval data published by AEMO is just the time-weighted average of the 6 x five-minute dispatch data points within a given trading interval. Hence, it is not until just after 25 minutes into a trading interval that the trading data for that interval can be known with certainty.

The generators are paid the variable trading price for net production in the half hour, and wholesale market customers (and hence indirectly the energy users) pay the variable trading price for energy consumed in each given half hour.

All data in NEM-Review is trading data.