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Carbon footprint process

Transpower’s carbon footprint reports are calculated in accordance with the Greenhouse Gas Protocol: A Corporate Accounting and Reporting Standard (GHG Protocol). The Protocol is the widely accepted methodology for carbon accounting, and is supported by ISO 14064.1 2006 Greenhouse gases Part 1: Specification with guidance at the organization level for quantification and reporting of greenhouse gas emissions and removals.  

Under the Protocol, emissions are divided into direct and indirect emissions, and reported under one of three “scopes”: 

• Scope 1: direct emissions controlled or owned by Transpower (e.g. fuel combusted in fleet vehicles),
• Scope 2: indirect emissions from consumed electricity, and
• Scope 3: other indirect emissions arising from the consequences of Transpower’s activities, but generated by sources not owned or controlled by Transpower (e.g. emissions arising from staff air travel).

Companies must separately account for and report on their scope 1 and 2 emission sources. Reporting on scope 3 emissions is optional.   

In defining our scope of assessment, we elected to apply the ‘equity share consolidation approach’. We sourced emissions information from our suppliers, and extrapolated where necessary. We applied the principles of relevance, completeness, consistency, transparency and accuracy to the assessment and report in accordance with the requirements of the Protocol.

For all emission sources (with the exception of sulphur hexafluoride) Transpower used the emission factors contained in the Ministry for the Environment document Guidance for Voluntary Corporate Greenhouse Gas Reporting: Data and Methods for the 2008 Calendar Year, released in 2009. These are considered to be the most up-to-date, reliable and accurate emission factor available for each product or emission source.  For sulphur hexafluoride, Transpower used the Global Warming Potential figure contained in the IPPC Guidelines (Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual, 2006).