NatHERS for existing homes trial

We’re running a field trial of the tools and processes used to rate the energy performance of existing homes before the program is formally launched from mid-2025. 

The trial is being run in partnership with CSIRO, on behalf of all states and territories, from late 2024 into 2025. 

There are two trial streams:

  • Core stream – where a trial assessor completes all elements of the assessment, including undertaking the NatHERS for existing homes training, collecting data on-site, and using the trial assessment tool to produce a home energy rating.
  • Scale stream – where banks partner with property valuers to collect data on-site and work with off-site NatHERS assessors to complete the assessment and produce a rating. 

Both streams support innovation in data collection and assessment by using mobile devices for collecting data in homes and the cloud-based energy rating tool developed by CSIRO called ‘AccuRate Enterprise’.

Register your home for an assessment

We are inviting eligible households to take part in the core stream of the trial. 

As a participant, you’ll receive:

  • A free home energy rating to learn how your home performs.
  • Practical tips for energy-efficient upgrades to save on energy costs and improve the comfort of your home.

How it works

  1. Register your interest.
  2. Get your home assessment – if eligible, a trained energy assessor will organise to visit your home to collect the data.
  3. Receive your energy rating certificate – you’ll be sent a trial certificate and tips for upgrading your home’s energy performance.

By joining the trial, you’ll help shape the future of residential energy efficiency in Australia. Don’t miss this opportunity to gain valuable insights into your home’s energy use and comfort.

Find out more and register now go to CSIRO’s registration page here.

Getting ready for a home assessment

Preparing for the assessment is simple. 

For homes participating in the core stream of the trials, an assessor will contact you to schedule a time to inspect your property. 

For scale stream participants appointments will be organised through participating companies.

During the visit, the assessor will evaluate all areas of your home, including attached garages and shading structures. 

To ensure the process runs smoothly, you should take the following steps before the assessment:

  • Make sure all rooms and areas are easily accessible and free of clutter.
  • Secure any pets and open window coverings to allow clear visibility.
  • If applicable, provide information about recent upgrades, such as insulation improvements or receipts for renovations.

These small steps will make the assessment faster and easier.

About your trial certificate

All participating households will receive a trial certificate from their assessor. The official Home Energy Rating certificate is still under development for the launch of NatHERS for existing homes, however, the trial certificate contains most features planned for the official version. These include: 

  • a NatHERS Star Rating (out of 10)
  • a Home Energy Rating (out of 100) 
  • a breakdown of the energy used by your appliances
  • estimates of your home’s annual energy use and greenhouse gas emissions 
  • the renewable energy profile for your home (if relevant).

You can use the trial certificate to:

  • Identify areas where energy efficiency and comfort can be improved.
  • Discuss potential upgrades with energy professionals or assessors.
  • Inform future home improvement plans, potentially increasing energy savings and comfort.

Your trial certificate cannot be used for regulatory compliance for new homes or major renovations.

About your ratings

NatHERS home energy ratings are a reliable guide to predicting and comparing the energy performance of homes. Information collected about your home and appliances is entered into a computer model which uses local climate data and standardised assumptions for occupant behaviour to predict the energy required to heat and cool your home and its overall energy performance. 

Your certificate contains two ratings: 

Star Rating

Homes are given a star rating between 0 and 10. This is based on the home’s heating and cooling needs, taking into account its local climate, design, materials and construction. This includes the:

  • layout of the home and its orientation
  • roof, walls, windows and floor, construction methods and materials and
  • shading from the sun's path and how well it takes advantage of local breezes.

Energy assessors use NatHERS computer modelling tools to predict the amount of heating and cooling your home will need to stay comfortable year-round. This is called thermal performance. 

 Below is a general guide to ratings:

  • A 0-star rated home is quite uncomfortable – too hot in summer and too cold in winter. It will require a lot of energy to heat and cool.
  • A home reaching a 7-star rating will need a small amount of mechanical heating and cooling to keep it comfortable to live in. This is the minimum standard for new houses under the National Construction Code 2022.
  • A 10-star home is very energy efficient. It will remain comfortable year-round, with little to no mechanical cooling or heating.

Home Energy Rating

Homes are given a home energy rating on a scale of 0 to 100. The home energy rating for existing homes is the same as the Whole of Home rating used for new homes and major renovations. 

The home energy rating builds on the thermal performance star rating by providing information about the energy use of your whole home. 

The rating considers the home’s thermal performance, energy used for heating and cooling, and major appliances, minus energy generated from solar panels, building a useful energy snapshot of energy costs as well as greenhouse gas emissions.

Appliances assessed as part of your home energy rating include: 

  • Heating and cooling
  • Hot water system
  • Lighting
  • Pool/spa pump
  • On-site energy generation and storage.

Homes with higher energy ratings cost less to run. They have better designs, efficient appliances and may also generate their own electricity.

While the Whole of Home rating scale ranges from 0 to 100 (where 100 is a net zero energy value home), ratings above 100 are possible. One way that a home may rate over 100 is where a home generates more energy than it uses.

How does your home compare? 

Most Australian homes were built before the introduction of minimum energy performance requirements. They were also designed with little consideration of the local climate which can significantly impact the energy efficiency and comfort of your home. 

Currently, the minimum star rating for a new home under the National Construction Code 2022 is 7 stars and the minimum Whole of Home rating is 60 out of 100 for houses and 50 out of 100 for apartments, noting this varies across the different states and territories.   

Home energy upgrades 

Quick wins such as draught proofing, better insulation, installing quality window coverings and external shading can improve comfort and reduce your energy bills. More extensive upgrades, such as full electrification of appliances and installing rooftop solar, can also save energy and money in the long term, but have higher upfront costs. 

The costs, benefits and feasibility of these options will vary for each home, depending on its construction and local climate.

You will receive upgrade advice with information on options to improve your home’s energy performance following your home’s assessment, alongside your trial certificate. 

Additional resources are available at: 


Trial technical documents

Several technical documents underpin the software used in the NatHERS existing homes trial, ensuring a robust tool and processes. 

It is important to note that the documents are for trial use only and will remain unchanged until updates are informed by trial findings prior to launch.

  • Technical Note – Provides a standardised approach to rating an existing dwelling. It details the requirements that must be followed for a NatHERS assessment in an existing home.
  • Guidance Note – Provides additional guidance to support the Technical Note. It presents information that can assist assessors to understand the requirements in the Technical Note.
  • Calculation Method – These documents outline the method that underpins the NatHERS Whole of Home appliance modules and rating, and this trial version has added considerations to account for calculating energy use in an existing home.
  • Thermal Standardisation and Specification – These documents ensure the tool incorporates specific data sets, fixed inputs, validation rules, and locks to ensure consistency and accuracy in thermal performance assessments for existing homes.

Each document is specifically marked as 'For use in Trials of Existing Homes Assessments' to ensure that trial participants and others are aware that these are not the finalised documents.

Household consent and information management

Participation in these trials is voluntary, and consent must be confirmed prior to any home assessment. CSIRO will collect and manage the consents of households on behalf of the trial partners. 

You can withdraw from the trial up to the time the assessor arrives at your home. After the assessment has been completed, it may be impossible for data to be removed from the study as it will have been deidentified.

For more information on how your privacy and household data is managed during the trial, see CSIRO’s Research Participant Information Sheet.

Contact us

For queries or support regarding NatHERS trials of existing home ratings, visit our helpdesk. Stay up to date with trials activities by subscribing to our newsletter.