In our system operator role, we work closely with industry and government to understand whether there is enough electricity to power New Zealand now and into the future.
Our security of supply work includes looking at:
- how much energy (or fuel) we have in the power system to meet New Zealand’s needs across a period of time.
- whether there is enough generation and transmission capacity to meet New Zealand’s electricity needs at any one point in time, such as on the coldest mornings and evenings.
Our most recent quarterly Security of Supply Outlook sets out our assessment of energy and capacity risks and mitigations through winter 2026. A range of other security of supply reporting and publications can be found on this page.
Security of Supply Assessment (SOSA) 2026
The Security of Supply Assessment (SOSA) is Transpower's annual ten-year assessment of New Zealand's electricity security of supply. It evaluates whether sufficient generation, storage, fuel supply and demand-side resources are expected to be available to manage dry winters and meet winter peak demand.
SOSA 2026 finds that electricity supply remains secure in the short term, provided committed generation and battery projects are delivered on time. However, increasing electricity demand, declining domestic gas supply, and potential delays to new generation projects create emerging dry-year energy risks later in the decade.
The assessment shows the New Zealand Winter Energy Margin is expected to remain above the lower security standard in the near term but falls below the standard by 2031 under the Reference Case, signalling a need for additional investment to maintain dry-year resilience. The South Island Winter Energy Margin and North Island Winter Capacity Margin remain above their security standards provided planned generation projects proceed as expected.
SOSA 2026 also introduces an Expected Future Case, reflecting a lower domestic gas supply outlook together with LNG imports from 2029. This indicates dry-year energy risks could emerge as early as 2028 before additional gas supplies become available.
The assessment highlights the importance of timely project delivery, maintaining flexible generation and fuel availability, and developing a diverse pipeline of new generation and demand-side resources to support New Zealand's future electricity needs.
Previous assessments can be found here.
System Operator Security of Supply Forecasting and Information Policy (SOSFIP) Review
We completed consultation in late 2025 on a draft proposal to amend the Security of Supply Forecasting and Information Policy (SOSFIP). The proposed changes aim to address evolving market conditions as the electricity system accelerates its transition towards increasing dependence on intermittent renewable generation, and risks to the availability of natural gas supplies to substitute for hydro generation during extended dry periods have increased.
Key amendments include improved forecasting tools, enhanced risk communication, updated contingent storage buffer settings, and expanded system risk considerations. Stakeholders broadly supported the changes, emphasising the importance of clarity, transparency, and timely information. The amendments are set to be implemented before Winter 2026, with minimal costs expected.
For further information, see the SOSFIP consultation page.
Security of supply reporting | |
| Market Operations Weekly Report | The Weekly Report is usually published on a Tuesday and provides key information about the electricity market and power system, generation mix and security of supply status. It is also used for system operator announcements and a market insight is included each week that drills into key industry topics. |
| Energy Security Outlook | This monthly report includes the Electricity Risk Curves (ERCs) and Simulated Storage Trajectories (SSTs). The ERCs reflect the risk of running out of hydro storage using a standardised set of assumptions. They take account of assumed availability of generation, fuels like coal and gas, as well as the impact of hydro inflow variation on hydro storage levels over time. The SSTs provide an indication to the market of the risks in crossing successive risk curves. |
| Quarterly Security of Supply Outlook | This document is published each quarter and provides the system operator’s assessment of the security of supply outlook for the next 12 months based on the latest Electricity Risk Curves (ERCs), New Zealand Generation Balance (NZGB), generation commissioning expectations, annual Security of Supply Assessment (SOSA), and observed operational conditions. |
| Annual Security of Supply Assessment (SOSA) | An assessment of balance between supply and demand in the electricity system over the coming decade. This helps generators, other market participants, investors and stakeholders understand security of supply risks and assists their decision making over things like building new generation. |
| New Zealand Generation Balance (NZGB) | This outage planning tool helps identify whether generation and transmission capacity is sufficient to meet peak demand over the coming six months throughout the country. |
| Hydro storage | This page is updated weekly and provides information on lake levels, inflows and contingent storage. |
| Market indicators | This page is updated weekly with demand profiles, the generation mix, HVDC transfer and prices, which can all indicate the market response to the current security of supply situation. |
Industry engagement | |
| System Operator Industry Forum | This is Transpower’s fortnightly discussion of current operational and market issues with industry in its system operator role. This is for electricity industry participants only. Email [email protected] if you would like to attend. |
| Industry workshops / webinar | Links to other system operator workshops and webinars for industry can be found here. |
Legislation, Policies and Plans | |
| Rolling Outage Plan | This plan provides for the management and co-ordination of planned outages as an emergency measure during energy shortages. |
| Emergency Management Policy (EMP) | The Emergency Management Policy (EMP), sets out the steps that we will take, as a reasonable and prudent operator, during an extended emergency. This includes the requirement for us to initiate an Official Conservation Campaign under pre-determined conditions and, if needed, manage and co-ordinate planned outages as an emergency measure in anticipation of, or during, prolonged energy shortages. |
| Security of Supply Forecasting and Information Policy (SOSFIP) | The Security of Supply Forecasting and Information Policy sets out our functions in relation to the provision of information and short to medium term forecasting. The latest approved SOSFIP is published on the Electricity Authority website here. A direct link to the document is here. |
| The Act | The Electricity Industry Act 2010 designates Transpower as the system operator. The Act also requires that as system operator we must provide information and short- to medium-term forecasting on all aspects of security of supply and manage supply emergencies. The Act is published on the New Zealand Legislation website and is administered by the Ministry of Business, Innovation, and Employment. |
| The Code | The Electricity Industry Participation Code 2010 (Code). It's the set of rules that governs nearly every aspect of the New Zealand electricity industry. |
| This document sets out key assumptions that the system operator must use in its Annual Security Assessment. The document is published on the Electricity Authority website. | |
More information | |
| System and Market Insights | Reports published here cover a range of power system and wholesale electricity market topics. They are typically technical in nature and designed for market participants but may be of use to wider audiences, including media, electricity consumers and other stakeholders. |
| Overview of security of supply | This page explains in more detail our approach to managing security of supply and how all the work we do fits together. |
| Learning material | This page has a range of learning resources that we have provided to help participants better understand security of supply |
| GOR Bus Split Principles and Guidelines | This document covers the principles of how the System Operator will use the Gore bus split that has been offered by the Grid Operator. |
| Managing 2024 security of supply risks | We set up a dedicated web page over winter 2024 to keep industry up-to-date with emerging security of supply risk related to hydro storage reaching historic lows. We are no longer updating this page but you can still access it here. |
| Media releases | System operator media releases related to security of supply can be found on Transpower’s News page. You can sign up to receive media releases here. |
| News from Transpower | The latest security of supply information may be included in Transpower’s monthly newsletter rounding up all the latest happening from across the business. You can subscribe to receive this here. |