Evolving market resource co-ordination: Tie-breaker provisions consultation
Submissions are now closed and cross submissions close 5pm Thursday 21 August 2025.
This consultation is to seek feedback on how tie-breaker situations should be resolved for multiple competing offers in the wholesale electricity market.
A tie-breaker situation arises when more, equally priced generation is offered at a single location than can be dispatched due to a network export limit. These situations are emerging in the market, and while not yet widespread or frequent, we are observing them in practice. As a consequence, generator owners and investors are increasingly seeking clarity and confidence on how tie-breakers are or will be resolved by the System Operator.
Your feedback will inform our decision on whether to progress to implement the proposed solution, (or a modified form of it), into our tools and processes. If we decide to proceed to implementation it could be in effect during the first half of 2026. If we instead decide to consider alternative options or approaches further, we are likely to re-consult on a different proposed solution.
Once we have considered the feedback we receive in response to this consultation we will publish our summary of submissions and the decisions we have reached having considered your feedback.
Consultation Documents
Providing feedback
Cross submissions should be emailed to [email protected] by 5:00 p.m. on Thursday, 21 August 2025. Please include the phrase “Evolving market resource co-ordination: Tie-breaker provisions” in the email subject line.
If your submission or cross-submission contains confidential material, please ensure this is clearly identified and provide a version of your submission or cross-submission that can be published. Transpower takes no responsibility for identifying confidential information.
Please note that all information provided to Transpower is subject to potential disclosure under the Official Information Act 1982.
Questions and System Operator Responses
- Dispatch Resolution in Zero-Priced Multi-Node Scenarios
Question
A participant asked:
In the tie-breaker consultation, it’s noted that scenarios involving multiple pricing nodes are outside its scope. A footnote explains that in such cases (e.g. regional), loss factors help establish deterministic MW allocations in forecast schedules, giving generators more certainty and enabling potential issues to be resolved ahead of real time.
Example scenario:
If all nodes in a region (e.g. Northland) are priced at $0.00/MWh and all generators have won the must-run auction:- Does the system solve multiple solutions across all nodes due to the zero price, and then randomly select generators across nodes to constrain?
- Or does it use loss factors to determine which node to constrain, and then randomly constrain generators at that node? If so, what loss factor is used—historical or expected for that half-hour?
Since the price is zero, it seems like the loss factor shouldn’t matter because the generation cost is zero.
System Operator Response
The dispatch system (SPD) applies a very small price (a fraction of a cent per MWh) to zero-priced offers during optimisation. This ensures it still aims to minimise total dispatched generation, even when all offers are at zero price. By doing so, SPD can use loss factors to guide scheduling decisions and minimise these very small costs. This is one of several penalty factors used to guide SPD toward more reasonable solutions. For example, SPD also penalises changes between real-time dispatch schedules, favouring solutions that are closer to the previous dispatch.
Solving a scenario where all zero prices are adjusted to a small positive value ensures that losses carry a cost, preventing overscheduling of losses and generation, while keeping the overall price effectively close to zero.
Losses between nodes are modelled using data from the Grid Owner, which allows SPD to calculate expected losses based on line loading. More details of loss modelling are available here: SPD 101.
Submissions
We received 7 submissions listed below
| Helios Energy | View |
| Lodestone Energy | View |
| Genesis | View |
| Mercury | View |
| Meridian | View |
| Ngawha Generation | View |
| PBA Consulting | View |