Transpower input methodologies
Input methodologies are the rules, requirements and processes that underpin regulation under Part 4 of the Commerce Act.
Current input methodologies for Transpower
The consolidated Transpower IMs determination below includes the input methodologies that apply for information disclosure regulation and Transpower Individual Price-Quality Path Determination 2025 [2024] NZCC 26. The consolidated Transpower IM below incorporates amendments contained in relevant amendment determination up to the consolidation as at 23 September 2026.
This consolidated Transpower determination includes input methodologies that apply for:
- information disclosure regulation from the commencement of disclosure year 2027; and
- an individual price-quality path that commences on or after 1 April 2030.
Historical amendments and consolidations
What are the IMs?
Input methodologies (IMs) are the rules, requirements and processes that underpin regulation under Part 4 of the Commerce Act. We must apply the input methodologies when we set price-quality paths and set information disclosure requirements. Regulated businesses are also required to apply the input methodologies.
The two IM determinations that apply to Transpower
The first is generally referred to as the Transpower Input Methodologies Determination (or the Transpower IMs for short). This covers matters such as how assets are to be valued, depreciated and revalued, how we estimate the cost of capital, how tax should be treated, and the allocation of common costs between Transpower's grid operator and system operator services.
The second is generally referred to as the capital expenditure input methodology (or the Capex IM for short). The Capex IM sets out the rules for Transpower proposing, and us assessing, Transpower's capital expenditure proposals.
The purpose of IMs
The purpose of IMs is to promote certainty for suppliers and consumers in relation to the rules, processes and requirements for regulation.
The Transpower IMs were originally determined in 2010, and the Capex IM was originally determined in 2012.
We are required to review the IMs at least every seven years. We substantially completed our first review of the Transpower IMs in 2016, and completed our first review of the Capex IM in 2018. We completed the second review of the Transpower IMs and Capex IM on 13 December 2023. You can find more information about these reviews below.
The reasons for the Transpower IMs and Capex IM are captured in the reasons papers for the original IM determinations and all subsequent amendment determinations – certain determinations and reasons papers can be found via the related pages.