We must apply the IMs when we set price-quality paths and set information disclosure requirements. Regulated businesses are also required to apply the input methodologies.

The IMs cover matters like how assets are to be valued, depreciated and revalued, how we estimate the cost of capital, how tax should be treated, and how common costs should be allocated where businesses provide both regulated and unregulated services.

The IMs also set out certain process requirements, as well as the rules relating to electricity distribution businesses applying for customised price-quality paths.

The purpose of IMs is to promote certainty for suppliers and consumers in relation to the rules, processes and requirements for regulation.

The IMs for electricity distribution businesses were originally determined in 2010 and there have been amendments made to the IMs since then.

We are required to review the IMs at least every 7 years. We completed our first review of the IMs in 2016 and are currently in the process of undertaking the 2023 review, you can find more information below.

The reasons for the current IMs for electricity distribution businesses are captured in the reasons papers for the original IM determination and all subsequent amendment determinations – these can be found via the links below.


2023 input methodologies review

We are in the process of reviewing the current IMs. Our review formally commenced on 22 February 2022.

Read more


Other past amendments and clarifications

These are the past decisions we have made related to input methodologies for Transpower, and the process of how we got to these decisions.

Read more


Current input methodologies for electricity distribution businesses

These are the current input methodologies that apply for electricity distribution businesses.