BASIX and NatHERS are often mentioned together in NSW residential projects, but they are not the same thing. BASIX is the NSW sustainability assessment framework used for residential development approvals. NatHERS is a national rating scheme used to assess the thermal performance of a home, including how much heating and cooling the dwelling is likely to need.
In simple terms, BASIX is the broader NSW certificate pathway. NatHERS is often used to support the thermal comfort part of that pathway. This is why many projects need both a BASIX Certificate and NatHERS thermal comfort modelling before the approval documentation is complete.
BASIX is a NSW sustainability assessment that covers water, energy use and thermal performance for residential development. NatHERS is a national thermal performance rating system that estimates how much heating and cooling a home is likely to need. In NSW, NatHERS is often used to complete the thermal comfort part of BASIX.
BASIX stands for Building Sustainability Index. It is a NSW sustainability assessment tool for residential development and forms part of the development application process in NSW. BASIX standards apply to residential dwelling types and cover water usage, energy usage and thermal performance.
A BASIX Certificate records the commitments a project must meet. These may include water efficient fixtures, rainwater tanks, hot water systems, heating and cooling systems, insulation, glazing, shading, ventilation and other design or system details. Because the certificate forms part of the approval documentation, the commitments should match the plans and specifications submitted for approval.
NatHERS stands for the Nationwide House Energy Rating Scheme. It is used to estimate the thermal performance of a home and the amount of heating and cooling the dwelling is likely to need. A higher NatHERS star rating generally indicates a home that needs less artificial heating and cooling to stay comfortable.
NatHERS modelling looks at the design of the dwelling, including orientation, climate, windows, insulation, shading, roof form, floor construction, wall construction and other building fabric assumptions. It does not replace the broader BASIX Certificate, because BASIX also includes water and energy commitments that sit outside the thermal comfort rating.
The main overlap is thermal comfort. BASIX includes a thermal performance section that aims to support comfort for occupants, reduce greenhouse gas emissions from artificial heating and cooling and reduce peak energy demand. NatHERS can be used as the simulation method for this part of BASIX.
When the simulation method is used, an accredited assessor models the dwelling using approved software and provides an assessor certificate. The NSW Planning Portal describes an accredited assessor as a person accredited by an Assessor Accrediting Organisation to conduct simulations for the Thermal Comfort Index of BASIX.
A practical way to understand the difference is this:
This is why NatHERS should not be treated as a replacement for BASIX. It is usually one part of the broader residential energy and sustainability compliance pathway.
Many NSW residential projects need a BASIX Certificate and may also require NatHERS thermal comfort modelling. The exact requirement depends on the project type, the approval pathway and the thermal comfort assessment method being used. New homes, dual occupancies, townhouses and more complex residential projects often need careful coordination between the BASIX and NatHERS components.
Some single dwellings may be eligible for the BASIX DIY thermal comfort method, where the project commits to minimum insulation levels and selects glazing and shading so estimated heating and cooling loads do not exceed the maximum loads set by BASIX. Other projects use the simulation method, where NatHERS modelling is carried out by an accredited assessor.
BASIX covers several sustainability commitments that are not simply part of a NatHERS thermal rating. These include water usage, energy systems and project commitments that sit beyond the building fabric itself. A project may need to include water efficient fixtures, rainwater tanks, efficient hot water systems, ventilation commitments, solar panels or other measures depending on the BASIX pathway.
Examples of BASIX commitments that may sit outside the NatHERS rating include:
NatHERS focuses on the thermal performance of the dwelling design. It estimates the heating and cooling loads that are likely to be required to keep the home comfortable. BASIX can use this information to satisfy the thermal comfort section of the assessment when the simulation method is used.
NatHERS modelling commonly considers:
BASIX and NatHERS should be coordinated because the same design decisions can affect both pathways. For example, glazing can influence thermal comfort, cooling loads, heating loads and the final commitments shown on the BASIX Certificate. Insulation, shading and construction systems can also affect whether the dwelling meets the required thermal performance outcome.
If BASIX and NatHERS are prepared separately without coordination, the project may end up with inconsistent assumptions. This can create confusion between the certificate, plans, window schedule, specifications and approval documentation. A coordinated assessment reduces the risk of rework and helps the project team understand which commitments need to be carried through to construction.
Because BASIX and NatHERS often appear in the same approval process, they are easy to confuse. The most common misunderstandings are:
Certified Energy prepares BASIX Certificates and NatHERS assessments for residential projects across NSW. Our team can review your plans, confirm the likely pathway and coordinate the BASIX and NatHERS components so that the certificate, thermal modelling and approval documentation remain aligned.
This is especially helpful for new homes, alterations and additions, secondary dwellings, dual occupancies, townhouses and multi dwelling developments where thermal comfort, glazing, insulation and system commitments need to be understood before lodgement.
Send your available plans to Certified Energy and our team can confirm whether your project needs BASIX, NatHERS or both.
Request a QuoteBASIX is the NSW sustainability assessment framework for residential development. It covers water, energy use and thermal performance. NatHERS is a national rating scheme used to assess the thermal performance of a dwelling, including how much heating and cooling the home is likely to need.
Many NSW residential projects need a BASIX Certificate and may also need NatHERS thermal comfort modelling as part of the BASIX pathway. The exact requirement depends on the project type, approval pathway and thermal comfort assessment method used.
No. NatHERS is not the same as BASIX. NatHERS focuses on thermal performance, while BASIX is broader and includes water, energy and thermal performance commitments for NSW residential development.
NatHERS can be used as the simulation method for the thermal comfort section of BASIX. In this pathway, an accredited assessor models the dwelling in approved software and provides an assessor certificate that supports the BASIX thermal performance outcome.