Wind Offer Arrangement (WOA) Project

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This programme of work was completed  October 2019

What’s WOA?

The objective of this project is to enable intermittent generators (wind farm owners) to withdraw their generation in an efficient, centrally coordinated way when the spot market price is below their short-run marginal cost (SRMC).


WOA will allow an intermittent generator to offer its generation to the spot market in a minimum of one and up to five price bands like most other types of generators, but with an extra field in the offer form called ‘forecast of generation potential’ (FOGP) for the estimate of the electricity (specified in MW) it will generate during a trading period. An intermittent generator must not generate electricity during a trading period at a rate that is more than 30 MW below the FOGP specified in its final offer for the trading period unless in order to comply with a constrained dispatch instruction issued by the system operator, or for a bona fide physical reason. WOA will also allow constrained on payments to be paid to intermittent generators, consistent with payments that are currently made to other types of generation.

Key communication dates


  1. Cut-over date for the transition to the new wind generation offer arrangements will take place at trading period 25 (12:00 noon) on 19 September 2019
  2. Traders must start submitting offers in the new format in the wholesale information trading system (WITS) at least 71 trading periods prior to the cut-over at trading period 25 on 19 September 2019.
  3. The new offer upload format will be available on WITS a week prior to the cut-over from 13 September 2019. At this time, intermittent generator traders may:  
    1. submit the new ‘forecast of generation potential’ for all trading periods 
    2. submit five price bands for trading period 25 on 19 September 2019 and subsequent trading periods
  4. Intermittent generator traders must:
    1. continue to offer a single price band for trading periods up to and including trading period 24 on 19 September 2019 under current offer price limits, i.e. $0.00/MWh (if must-run) or $0.01/MWh, and
    2. include the new ‘forecast of generation potential’ in offers for trading period 25 on 19 September and all subsequent trading periods. Offers not compliant with this requirement will be rejected by WITS
  5. From TP 25 on September 19th the way dispatch constraints on intermittent generation in real time dispatch are removed will be changing. This animation video on the Transpower YouTube channel explains this change.
  6. Intermittent generation owners must have come to an agreement with the Grid Owner on the provision of metering data as specified in the Wind Offer Arrangements gazetted code amendment no later than 10 September 2019 and must be continuously providing this data from that date. The applicable code amendment can be found on the Electricity Authority website at the following location:
  7. Note also that the WITS manager has advised that due to the way the existing WITS rollover process works (offers for the current day will be rolled over to the following two days) participants must ensure that all 'Wind Generation' offers submitted contain the FOGP value from the following dates onwards:-
    Deadline Date Deadline Time  Task  Trading  Date From
    16/09/2019 23:59:59 to include FOGP for 19/09/2019 (TP25)
    17/09/2019 23:59:59 20/09/2019 (TP1)
    18/09/2019 23:59:59 21/09/2019 (TP1)

    All wind generation offers from TP25 on 19 September must include a FOGP value so that any offers that are rolled over from that date will include those FOGP values

  8. For any questions relating to the provision of this metering data please contact Josh Wairau at or by phone on 04 590 6831

Related information


  1. The revised SPD formulation can be found on the Software Specifications page on the Transpower website
  2. Background and other explanatory information previously published by the Electricity Authority
    1. Gazetting Notice
    2. Consultation
    3. Decision


If you have any concerns or questions after the change has been deployed, please contact Market Operations during business hours on (04) 5907470 or