When is NGER uncertainty reporting required?

What uncertainty means

Uncertainty is the range within which the true value of an emissions estimate is expected to fall. NGER requires it at a 95% confidence level, and estimates need only provide for statistical uncertainty. The Measurement Determination draws on the GHG Protocol guidance on uncertainty assessment published by the World Resources Institute and the World Business Council for Sustainable Development.

How it is assessed

Section 1.14 of the NGER Measurement Determination requires every emissions estimate to include an assessment of uncertainty in accordance with Chapter 8. The accuracy principle in section 1.13 requires uncertainties to be minimised, so that estimates are neither over nor under the true values at a 95% confidence level. In EERS, selecting the auto-calc option calculates and displays uncertainty as a percentage for the source or fuel.

An illustration

A facility whose diesel combustion produces 30,000 t CO2-e of Scope 1 emissions in a year must report uncertainty for that diesel. If the same facility’s LPG use produces 2,000 t CO2-e, uncertainty for the LPG does not need to be reported. The test is applied to each fuel or source separately, not to the facility total.

Below the trigger

Below 25,000 t CO2-e for a fuel or source, uncertainty does not have to be reported. The estimate must still meet the general principles of transparency, comparability, accuracy and completeness in section 1.13.

Why it matters

Uncertainty depends on the method and measurement criteria behind an estimate, so for the largest sources it is a direct signal of data quality to the Regulator and to auditors.