Ready, set, benchmark! NatHERS for existing homes now live.

For new housing the use of the National Home Energy Rating System (NatHERS) to target and verify energy and thermal performance is baked into the National Construction Code as a requirement. However, the roughly 90 per cent of housing that predates minimum energy standards has missed out.

According to research including a 2022 report by the by the Climate Council, Tents to Castles: Building energy efficient, cost saving Aussie homes, implementing energy ratings is a necessary first step.

“Greater energy efficiency means fewer greenhouse gas emissions, which is essential for tackling climate change,” writes co-author, economist Nicki Hutley.

“But that’s not where the benefits of making homes more comfortable to live in stops: we can also improve people’s health and wellbeing, reduce electricity bills, strengthen our energy grid and create jobs.”

The backstory

The launch of NatHERS for existing homes by the Commonwealth Department of Climate Change, Energy, the Environment and Water (DCCEEW) addresses some of the key recommendations experts have been making.

It was first trialled in partnership with CSIRO and four major banks from 2024 to early 2026, with more than 1,000 free home energy rating assessments delivered across a wide range of climate zones and existing dwelling types.

The report on the phase one trial can be accessed here.

In addition, a public consultation was held that invited feedback from stakeholders including advocacy groups, industry associations, product and appliance manufacturers, community groups and property industry bodies including social housing organisations.

Now out in the market, the tool provides a means to assess and report the energy efficiency of an existing home while also identifying opportunities for improvement that deliver both bill savings and thermal comfort.

Expert perspective from HIP V. HYPE

David Mahony, Director and Head of Better Buildings (ESD) at HIP V. HYPE tells HVAC&R News it will support positive change.

“(It is) similar to what made NABERS effective for commercial buildings,” Mahony says.

“You can’t manage, or price, what you can’t measure. The existing housing stock is currently an information vacuum, and a tool like NatHERS for existing homes can help to start closing that gap.”

He identifies several ways the availability of benchmarking then translates into improvements, including the all-important price signal.

“Once ratings are visible at point of sale or lease, we may start to see that efficient homes demand a premium while inefficient ones attract a discount,” he says.

This could help turn retrofit into an investment decision with a visible return, not only through focusing on aesthetic features such as a marble benchtop but also the “invisible” improvements such as insulation in a roof or wall cavity.

Mahony suggests that the government’s partnership with major banks during the Phase One trial suggests that there may be a move towards “green” mortgage products.

“And potentially risk-adjusted insurance given the possible links to climate change resilience. This creates a second capital-market pathway, independent of sale price.”

There is also a policy leverage aspect, he observes.

“A national, comparable metric makes it possible to embed performance into incentive schemes, mandatory disclosure regulation, or building-related tax and rebate settings, which is a far stronger lever than voluntary comfort or energy-bill arguments alone.”

How can owners use the information?

Knowledge is power, and there are some easy retrofit wins home owners may become inspired to undertake.

“Ideally the tool will inform retrofit works with a focus on reducing operational energy consumption, while also helping better-performing homes stand out at point of sale or lease, thus allowing the market to build demand for better homes,” Mahony explains.

“The most likely easy wins for retrofits include adding ceiling insulation, draught sealing (improving airtightness), and upgrading to double glazing or installing secondary glazing or films, alongside more efficient air conditioning, domestic hot water systems, and appliances, plus PV (photovoltaic) installation.

“These retrofits, particularly building fabric upgrades, are also an opportunity to improve both the thermal performance and the ventilation of our homes, provided they are treated as whole systems.

“By pairing efficiency and airtightness measures with considered moisture management and ventilation, we can lift energy performance and occupant health together, and avoid the unintended consequences seen where other countries pursued energy efficiency in isolation.”

In the UK, Canada, USA, NZ Germany and some Australian new builds, he explains there have been cases where energy efficiency approaches and increased airtightness result in issues including mould, moisture and microbial exposure.

“Given this international track record, occupant health and the hygrothermal performance of homes, particularly condensation and mould risk, deserve careful consideration whenever retrofit works touch the building’s thermal envelope,” Mahony says.

“This isn’t only a NatHERS tools issue. It’s a broader one, requiring professionals assessing existing homes and contractors carrying out retrofit work to have the knowledge needed to manage these risks.”

Can it help accelerate electrification?

Mahony says the Whole of Home component of the NatHERS rating will “favour electric appliances and services over gas-powered systems”.

“While this alone is unlikely to be enough to convince a portion of the population that electrification benefits their wallet, their health, and the planet, it does provide an easy-to-communicate basis for comparison and benchmarking,” he says.

In general, the release of the tool does help progress sustainability and liveability.

“It is a step in the right direction, given how poorly a significant portion of our current building stock performs,” Mahony says.

“The data NatHERS for existing homes will generate is significant for both industry and policymakers in supporting the improvement of existing buildings. I expect this will bring increased awareness in industry and across consumers.

“However, at the same time, I believe that these schemes work best when enforced by strong legislation that supports their implementation and keeps relevant parties accountable.”

While it is also known there is often a gap between the design performance of a dwelling and the final occupied performance, there are no known plans for NatHERS for existing homes to be used as a verification of performance for new builds.

“I expect its impact on new-build quality to be minimal, at least in the near term,” Mahony says.  

It’s not set-and-forget

Research is ongoing to improve both the data behind the tool and the quality of insights it can deliver.

“The current research that the CSIRO is undertaking to better understand occupant behaviour and building use, and to translate that into improved software assumptions, will be critical to improving the tool’s reliability and to helping close the performance gap that exists between modelled results and operational performance,” Mahony observes.

Get your hands on the toolkit

DCCEEW has launched a new website domain, Home Energy Rating, which is the portal for assessors, homeowners and stakeholders to access resources including:

• Technical Information for assessors and access to training and accreditation for new assessors
• Information for builders, lenders, insurers, software providers and real estate agents
• Information for owners including how to get an assessment and how to improve a rating
• Information for renters, who have the right to obtain a Home Energy Rating; this section also foreshadows possible introduction of mandatory disclosure of ratings at point of lease
• A library of technical reports, guides, forms and related policy documents.

Get started here.

Image: Director and Head of Better Buildings (ESD) at HIP V.HYPE, David Mahony. Photo courtesy HIP V. HYPE.

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