(image from NatHERS Whole of Home tool explanation video available on Youtube)
Australia’s Nationwide House Energy Rating Scheme (NatHERS) is expanding to cover existing homes, marking a major milestone in improving the energy performance of Australian residential buildings. This extension builds on the current framework used for new homes and introduces assessments tailored to the needs of older housing stock. Given that many homes were built before energy efficiency standards were enforced, the scheme offers significant potential to reduce emissions, cut energy costs, and enhance comfort for the more than 10.8 million existing residential dwellings.
In this post, we’ll dive into the NatHERS for existing homes scheme’s design, the role of its pilot program, mandatory disclosure, and its interaction with existing tools such as the Residential Efficiency Scorecard. We’ll also look at what’s next as the scheme moves toward full-scale rollout in 2025.
What’s Changing with the NatHERS Expansion
Until now, NatHERS has focused solely on providing a star rating for new residential dwellings. The new expansion to existing homes introduces both thermal and a broader, whole-of-home energy performance approach, building on recent updates to NatHERS software tools. The expanded scheme will assess not only the thermal shell but also the performance of fixed appliances, on-site energy generation (like solar PV systems), and storage solutions.
The launch of NatHERS for existing homes will, at a minimum, consist of:
- The NatHERS existing homes Benchmark Tool
- a software accreditation protocol and calculation method for tool developers
- an initial pool of trained and accredited assessors
- the release of other key elements such as the Training and Skills Strategy and Assurance Strategy.
Following the launch for existing homes, efforts will then be focused on:
- potential accreditation of third-party user interface tools
- increasing the functionality of energy rating tools
- implementing the Training and Skills Strategy
- scaling up the pool of assessors
- enhancing functionality and accessibility to increase program scale to support potential disclosure schemes.
Why NatHERS for Existing Homes Matters
Australia’s existing housing stock offers a massive opportunity for energy savings. Research suggests that most existing homes have energy ratings below 3 stars, with improvements to even 5 stars reducing heating and cooling energy use by around 40%. The new NatHERS framework aims to address these gaps, delivering the following benefits:
- Lower Energy Costs: Energy-efficient homes reduce the need for heating and cooling, saving households money.
- Healthier Living Spaces: Improved insulation and ventilation create more comfortable indoor environments and reduce risks from extreme temperatures.
- Environmental Impact: By enhancing the energy efficiency of homes, the scheme contributes to Australia’s 2050 net-zero emissions target.
- Financial Incentives: The ratings will facilitate access to green loans and grants, incentivizing homeowners to invest in energy upgrades.
National Agreement and Pilot Rollout
The expansion of NatHERS has been agreed upon by building ministers across all states and territories. However, the timing of rollout will vary, as each state decides how to integrate the scheme into local energy legislation and policies. Some regions may adopt the scheme sooner than others, depending on infrastructure readiness and policy alignment. We also can’t rule out good old politics as well, which may potentially delay implementation in particular jurisdictions.
This staggered rollout reflects the complexity of managing both voluntary and mandatory disclosure schemes, which require coordination across multiple levels of government. NatHERS will underpin these disclosure schemes, helping buyers and renters understand the energy performance of homes at the point of sale or lease. However, banks, valuers, real estate agents and financing bodies also play a significant role in this change.
The pilot program for the NatHERS expansion to existing homes is already underway, testing the framework before its broader rollout in 2025. The pilot aims to refine processes for both the core and scale streams. The pilot program also tests the practical aspects of assessments by engaging homeowners, assessors, and stakeholders to ensure the process is efficient, consumer-friendly, and scalable. Feedback from these early assessments will shape the final design, ensuring that the scheme is ready for nationwide implementation. The pilot will also explore how recommendations for upgrades and financial incentives can be seamlessly integrated into the program, encouraging homeowners to take action and enhance their home’s energy performance.
There are two streams of existing homes energy performance assessment planned for the trial:
• Core stream – trial assessors complete all elements of the assessment, including on-site data collection and the use of the trial energy rating tool to produce a rating and provide upgrade advice to trial households. The trial assessors from the Core stream will become the initial pool of NatHERS assessors for existing homes at launch.
• Scale stream – property valuers perform on-site data collection and NatHERS accredited assessors (for new homes) complete the assessment off-site and produce a rating. No upgrade advice will be provided. This stream will test a possible approach to delivering ratings for mandatory disclosure fast, at scale and at low cost while still ensuring reliability and consistency of results.
As part of the pilot, MagicPlan and a set of customised forms, will be used to collect building geometry on site. Other laser measurement tools that connect to phones and tablets via Bluetooth may also be used. Data will be collected onsite and then sent to an energy assessor back in the office who will undertake the actual NatHERS for existing homes assessment. Assessments will be undertaken during the pilot using Accurate Enterprise (known as Accurate Enterprise – Existing or AEE), which has been modified to apply to existing homes.
An existing homes Technical Note has been developed by the NatHERS Administrator, supported by a Guidance Document, which mirrors the approach taken with the existing NatHERS for New Homes.
NatHERS is currently developing a technical specification for software developers, and it is expected that as we move closer to the rollout in 2025 we will start to see software developers such as Hero enhance their existing products to allow Existing Home assessments in the same platform as assessments of new homes.
In time I would fully expect to see multiple methods to collect data, including the use of tools such as Matterport, the upload of plans (similar to new homes), and possibly even the reuse of an existing file from an assessment of the home when it was new.
Will Existing Home Ratings require mandatory disclosure?
A key component of the NatHERS expansion to existing homes is the introduction of mandatory disclosure of energy ratings at the point of sale or lease. This means that buyers and renters will be informed of a property’s energy performance upfront, enabling more informed decision-making. This system has the potential to drive significant improvements in the housing market by incentivizing energy upgrades to make homes more appealing and competitive.
However, the rollout of mandatory disclosure will likely face challenges, particularly in terms of coordination across states and sectors and a need to significantly increase in the number of assessors nationally. To ensure a smooth transition and achieve maximum impact, I would speculate that that state governments may prioritize ratings of public housing as a starting point. Public housing represents a significant portion of Australia’s housing stock and typically houses vulnerable populations who stand to benefit the most from improved energy performance. By starting with public housing, governments can ensure energy efficiency upgrades deliver tangible improvements in health, comfort, and energy savings for low-income households while setting a precedent for the broader market. With government as the landlord, some may argue that they have both a duty of care and a moral obligation to do so.
A phased approach—beginning with government-owned properties—will also allow policymakers to gather data, refine the process, and build the infrastructure needed for a successful, nationwide mandatory disclosure program across the private market.
What Happens to the Residential Efficiency Scorecard?
The Residential Efficiency Scorecard, developed by the Victorian Government, has been a widely used tool for assessing the energy efficiency of existing homes. It provides homeowners with an easy-to-understand star rating based on the energy performance of their house, along with recommendations for upgrades. With the upcoming NatHERS expansion, many stakeholders have wondered how these two programs will interact.
The intention is not to replace the Residential Efficiency Scorecard immediately but rather to align it with the expanded NatHERS framework over time. The two programs share similar goals—providing households with actionable advice to improve energy efficiency—but the NatHERS expansion offers a more standardized national approach, which could gradually supersede state-based tools like the Scorecard.
While NatHERS will underpin the national energy efficiency disclosure framework, tools like the Scorecard may still play a complementary role, particularly in regions like Victoria where the program is already well established. This could mean Scorecard assessments remain useful until NatHERS fully integrates into the national disclosure framework and provides a unified certificate recognized across all states.
Preparing for the NatHERS Existing Homes Scheme
The NatHERS Administrator is establishing arrangements for Accreditation bodies, and has recently released an Expression of Interest (EOI) calling for submissions. These organisations will be known as Assessor Support Providers (ASPs). I fully expect the three existing new home Accredited Assessor Organisations (AAOs) will apply to also be ASPs.
Accredited assessors will play a vital role in the scheme by:
- Guiding homeowners through the assessment process.
- Providing upgrade advice based on the home’s current performance.
- Ensuring that households receive accurate ratings and access to appropriate financial incentives.
Assessors will require specific training and to pass a specific exam in order to become accredited. Training programs and guidelines are being refined as part of the pilot phase to ensure the smooth transition of assessors into the expanded scheme.
A new unit of competency is being developed focused on assessing residential buildings under the NatHERS for existing homes scheme and will in time form part of the Certificate IV in Home Energy Efficiency and Sustainability. I would expect that assessors who want to become accredited for existing homes would have to undertake training in:
- The new unit of competency
- Any new tools that will be used for existing homes assessments
Looking Forward: What’s Next?
The full rollout of NatHERS for existing homes is expected by mid-2025. In the meantime, feedback from the pilot program will shape the final design of the scheme. Homeowners and assessors are encouraged to stay updated on state-specific timelines and emerging financial products, such as grants and green loans, that will support energy upgrades.
By expanding NatHERS to existing homes, Australia is taking a significant step toward a more sustainable future. The new ratings will empower households to reduce energy use, cut emissions, and improve comfort, all while contributing to the national goal of net-zero emissions.
The NatHERS expansion presents a tremendous opportunity to upgrade Australia’s housing stock systematically. As the pilot phase continues, additional guidance and updates will be released to help homeowners and assessors prepare for full-scale implementation in mid-2025. Meanwhile, assessors and homeowners should stay informed about state-specific timelines and emerging financial incentives that may accelerate upgrades.
This transition will also complement existing programs, such as minimum rental standards and grants aimed at low-income households, to ensure that all Australians can benefit from more energy-efficient homes.
For more information and updates, visit the NatHERS website or follow ongoing discussions through the CSIRO and DCCEEW consultation hubs. You can view a video about NatHERS existing homes tool here – https://youtu.be/ZvbEceVHfDg?si=6kAh_MuKsUvLZa4F
