NatHERS for existing homes trial report

The Australian Government, on behalf of all states and territories, delivered a successful national field trial of home energy ratings for existing homes from 2024 to early 2026. 

The trial was conducted in partnership with the CSIRO, energy assessors, and the finance sector. It delivered more than 1,000 free assessments across a broad range of climates and dwellings. 

The trial’s aim was to identify what works in practice and what needed to be strengthened to support a staged rollout of existing home energy ratings. It found NatHERS for existing homes is a viable, fit-for-purpose scheme and should be fully implemented.

The trial tested two delivery approaches: 

• Core stream – where trained trial assessors complete all elements of the assessment, including collecting data in the home, and using the trial assessment tool to produce a home energy rating and trial certificate.
• Scale stream – where banks partnered with property valuers to collect the data in the home and then NatHERS assessors worked off-site to produce a home energy rating and trial certificate.

The trial focused on: 

• testing whether the tools can produce reliable and comparable ratings
• how the delivery approaches can fit within property and lending processes
• confirming that training and support services are sufficient to enable consistent data collection and application of the technical guidance.

Read the report from the trial here. 

The findings from the trial informed many of the enhancements being implemented as part of Stage 2 of NatHERS for existing homes and beyond, including:

• updates to software tools that reduce overall assessment time
• release of an updated Home Energy Rating certificate, featuring clearer and more tailored upgrade recommendations for each property
• improved training and supporting materials to enhance assessor capability and consistency introduction of a data collector training and accreditation pathway (under development)