Residential Performance
Clear guidance on NatHERS assessments, residential energy ratings and thermal performance requirements for new homes across Australia.
Understand when NatHERS applies, how current 7 Star requirements influence design and how the assessment connects with BASIX, Whole of Home and new home energy compliance.
Send Your Plans for ReviewIn Brief
A NatHERS assessment uses accredited thermal modelling software to assess the thermal performance of a new home or dwelling design. It estimates how much heating and cooling energy the dwelling is expected to require to remain comfortable, based on its building envelope, layout, orientation, construction and local climate.
NatHERS stands for the Nationwide House Energy Rating Scheme. It is commonly used for new homes, townhouses and apartments as part of the residential energy compliance process. The thermal model considers insulation, glazing, shading, orientation, construction materials and climate response, with the result expressed as a rating from 0 to 10 stars.
A 7 Star NatHERS rating is a thermal performance outcome within the NatHERS framework, not a separate assessment system. Depending on the project location and approval pathway, NatHERS may operate alongside requirements such as BASIX, while Whole of Home considers household appliances and energy systems beyond the thermal star rating.
The dwelling’s building envelope, layout, orientation, insulation, glazing, shading, construction materials, ventilation assumptions and response to the local climate.
It is commonly used for new residential projects that need to demonstrate dwelling thermal performance or support energy-efficiency compliance.
7 Star is a thermal performance outcome produced within NatHERS and is an important benchmark for many current new-home projects.
Knowledge Hub
This guide explains how NatHERS assesses the thermal performance of new dwellings, how star ratings are produced and how building envelope, design and climate influence the assessment outcome.
A clear explanation of the Nationwide House Energy Rating Scheme and how it applies to new residential projects.
How NatHERS considers the dwelling layout, orientation, glazing, insulation, shading, ventilation assumptions and local climate.
What a NatHERS star rating means and how the 0 to 10 star scale reflects dwelling thermal performance.
How 7 Star relates to NatHERS as a current thermal performance benchmark, rather than a separate assessment system.
How the former 6 Star benchmark compares with the current 7 Star context within the broader NatHERS framework.
How NatHERS is used nationally while residential approval and compliance pathways can vary between states and territories.
Why location and climate data influence the heating and cooling loads calculated through a NatHERS assessment.
How orientation, window design, insulation, air leakage assumptions, shading and thermal mass can shape the rating.
How a NatHERS thermal assessment may connect with BASIX requirements for residential projects in NSW.
The distinction between NatHERS thermal-star modelling and the assessment of fixed appliances and household energy systems.
Where NatHERS commonly applies across new houses, townhouses, apartments and certain residential alteration projects.
The plans, specifications, glazing details and building-envelope information usually needed for thermal modelling.
How a NatHERS assessment usually moves from document review to thermal modelling, star rating and certification.
How early building-envelope and design decisions can improve the NatHERS result before the project reaches approval stage.
Clear answers to common questions about NatHERS assessments, star ratings, certificates, modelling and project requirements.
Foundations
NatHERS stands for the Nationwide House Energy Rating Scheme. It is Australia’s residential thermal energy-rating framework and is used to assess how effectively a dwelling design and building envelope respond to the local climate.
A NatHERS assessment uses accredited thermal modelling software to estimate the heating and cooling energy a dwelling is expected to require to remain comfortable. The result is expressed as a star rating from 0 to 10 stars, with a higher rating generally indicating stronger thermal performance.
NatHERS is commonly used for new houses, townhouses and apartments, as well as certain residential alteration and addition projects. It can support residential energy-efficiency compliance under the broader building compliance framework and, in NSW, may connect with BASIX requirements for residential projects.
In simple terms: NatHERS is the system used to model and rate the expected thermal performance of a new dwelling before it is built. The assessment produces a star rating, with outcomes such as 7 Star NatHERS reflecting the performance achieved by the dwelling design.
Thermal Performance
A NatHERS assessment models the thermal performance of a dwelling. It estimates the heating and cooling energy the dwelling is expected to require to remain comfortable throughout the year, based on the design, construction and climate information entered into accredited NatHERS software.
The assessment considers how the building fabric works as a whole. This includes the dwelling’s layout, orientation, insulation, glazing, shading, roof and wall construction, floor type, ventilation and air-leakage assumptions, thermal mass and local climate conditions.
The NatHERS thermal star rating does not represent every part of household energy use. It focuses on the dwelling’s calculated heating and cooling loads. Fixed appliances and systems such as hot water, lighting, heating and cooling equipment, pools, solar generation and batteries are considered through related assessment areas such as Whole of Home energy performance.
In simple terms: NatHERS models how effectively the dwelling design and building envelope help maintain comfortable indoor temperatures, and calculates the expected heating and cooling loads. For the assessment of fixed appliances and household energy systems, see Whole of Home.
Star Ratings
A NatHERS star rating is the result produced by thermal modelling of a dwelling design. The rating runs from 0 to 10 stars and reflects the calculated heating and cooling energy the dwelling is expected to require to remain comfortable.
A higher star rating generally means the dwelling design and building envelope respond more effectively to the local climate and are expected to require less heating and cooling energy. A lower rating indicates higher calculated heating or cooling loads are likely to be needed to maintain comfortable indoor conditions.
The star rating is focused on the thermal performance of the dwelling design. It is not a prediction of household electricity bills and does not assess every part of the home’s operational energy use. Fixed appliances and energy systems are considered separately through areas such as Whole of Home.
Higher heating and cooling loads are calculated for the dwelling to maintain comfortable indoor conditions.
The dwelling design is expected to perform better thermally and require less heating and cooling energy. See how design changes can help improve a NatHERS rating.
7 Star is a thermal performance outcome within NatHERS, not a separate assessment system.
The rating represents modelled thermal performance, not actual day-to-day energy use, occupant behaviour or future electricity costs. See Whole of Home for the broader energy context.
7 Star NatHERS
7 Star NatHERS means that a dwelling design has achieved a 7 star thermal performance result under the Nationwide House Energy Rating Scheme. It is a rating outcome produced through a NatHERS assessment, not a separate assessment system.
A 7 star rating generally indicates lower calculated heating and cooling loads than earlier minimum benchmarks. The result reflects how effectively the dwelling fabric and design respond to the local climate, including orientation, insulation, glazing, shading, ventilation assumptions and construction type.
For current new-home projects, 7 Star is an important residential thermal performance benchmark. Whether a dwelling reaches that result depends on the complete NatHERS model rather than any single material or design feature. Early assessment can help identify thermal performance issues while the design can still be adjusted.
This section provides the benchmark context within the wider NatHERS system. For a more focused explanation of current requirements and the transition from earlier standards, see our supporting guide to 7 Star Energy Ratings. For historical comparison, you can also read about 6 Star vs 7 Star NatHERS ratings.
The assessment framework is NatHERS. 7 Star is a thermal performance result achieved within that framework.
7 Star represents an important current benchmark for many new dwelling projects, subject to the applicable jurisdiction and approval pathway.
Orientation, glazing, insulation, shading and construction choices can influence the modelled result. See the main design factors.
A 7 Star Energy Rating remains part of the broader NatHERS star rating pathway rather than a different thermal assessment system.
Rating Benchmarks
6 Star and 7 Star are thermal performance outcomes within the NatHERS framework. They are not separate assessment systems. NatHERS is the thermal modelling and rating system, while the star result reflects the calculated heating and cooling performance of the dwelling design.
For many years, 6 Star NatHERS was the minimum benchmark associated with many Australian new-home projects. Under newer residential energy-efficiency settings, 7 Star has become the relevant thermal performance benchmark for many new dwellings, subject to the applicable jurisdiction, building classification and approval pathway.
Six Star is therefore most useful as historical and comparison context. It helps explain the transition toward higher-performing dwelling fabric and lower calculated heating and cooling loads, while current projects should be assessed against the requirements that apply to their location and approval pathway. For a focused comparison, see our guide to 6 Star vs 7 Star NatHERS ratings.
6 Star is primarily relevant to earlier requirements, older projects and comparisons showing how residential thermal performance benchmarks have changed.
7 Star is an important current benchmark for many new dwelling projects within the NatHERS pathway. See the full 7 Star Energy Rating guide.
In simple terms: NatHERS is the assessment system. 7 Star is an important current benchmark for many new dwellings, while 6 Star mainly provides historical and comparison context.
National Context
NatHERS is Australia’s national residential thermal energy-rating framework. The same overall assessment framework is used across the country, although the way a NatHERS certificate connects with approval documentation can vary between states and territories.
Across Australia, NatHERS thermal modelling can support residential energy-efficiency compliance under the National Construction Code. The applicable pathway can depend on the project location, building classification, approval stage and jurisdictional requirements. For project timing context, see when NatHERS is commonly needed.
In NSW, a NatHERS assessment may connect with BASIX requirements for residential projects. In other states and territories, the NatHERS rating and certificate may form part of different building approval or residential energy-efficiency documentation processes.
The NatHERS assessment remains focused on the thermal performance of the dwelling design, including its building envelope, heating and cooling loads and response to the local climate. What changes between jurisdictions is generally the surrounding approval pathway, including the required project documents and the point at which the assessment process must be completed.
Project note: Certified Energy can review residential plans and specifications for projects across Australia, identify how NatHERS relates to the applicable approval pathway and confirm the information needed to begin the thermal assessment.
Climate Response
NatHERS is climate specific. A dwelling design is not assessed in isolation from its location. The thermal model uses climate data applicable to the project location and considers how the dwelling responds to seasonal heating and cooling conditions.
This is why the same dwelling design can produce different thermal performance results in different parts of Australia. A design that performs well in a warm coastal climate may require different glazing, shading, insulation or air-movement responses in a cooler, hotter, drier or more variable climate. For a practical explanation, see our guide to NatHERS climate zones.
Climate data also helps explain why NatHERS is closely connected to building-envelope and design decisions. Orientation, window placement, solar gain, shading, thermal mass, ventilation and air-movement assumptions, and insulation are all assessed in relation to the local conditions. This is why climate responsive design matters for NatHERS.
NatHERS uses climate data to calculate how the dwelling is expected to perform in its project location, rather than applying one generic thermal result across Australia.
An effective design response depends on the climate. Glazing, shading, insulation, air-movement assumptions and construction choices all influence the calculated heating and cooling loads.
In simple terms: NatHERS ratings are shaped by climate. The same dwelling design may need different building-envelope and design responses depending on where it is built. See the main design factors that affect a NatHERS rating.
NSW Projects
NatHERS and BASIX are related, but they perform different roles. NatHERS is a software-based thermal energy-rating pathway for dwellings. BASIX is a separate NSW planning and sustainability framework for residential development.
For relevant NSW projects, a NatHERS assessment may be used to demonstrate the thermal performance of the dwelling design within the applicable BASIX pathway. The NatHERS model remains focused on the building envelope and calculated heating and cooling loads, while BASIX addresses a broader set of NSW project requirements.
The way the two systems connect depends on the project type, scope of works, approval pathway and documentation requirements. A NatHERS assessment should therefore be understood as the thermal rating component where that pathway applies, rather than as a replacement for the broader BASIX process. See when NatHERS is commonly needed and what project documents are usually required.
The NSW planning and sustainability framework within which thermal performance and other residential project requirements may need to be demonstrated. Read the full BASIX guide.
The thermal modelling and star-rating pathway used to calculate the dwelling’s expected heating and cooling performance. See what NatHERS measures.
In simple terms: BASIX is the broader NSW project framework. NatHERS is the thermal modelling and star-rating pathway that may be used to demonstrate dwelling thermal performance within that framework. The assessment process depends on the project type, approval pathway and documents available.
Broader Energy Use
NatHERS and Whole of Home are connected, but they address different parts of residential energy performance. The NatHERS thermal star rating reflects the calculated heating and cooling loads of the dwelling design, based primarily on its building envelope and response to the local climate.
Whole of Home extends beyond the thermal star rating to consider fixed appliances and household energy systems. Depending on the applicable pathway, this may include heating and cooling equipment, hot water, lighting, cooking, pool and spa equipment, and on-site energy generation. The broader methodology is explained in the Whole of Home Knowledge Hub.
The distinction is therefore important. NatHERS models how the dwelling fabric performs thermally, while Whole of Home considers energy use associated with fixed systems and equipment beyond that thermal result.
Improving a NatHERS rating generally involves changes to the dwelling layout, orientation, glazing, insulation, shading or construction. Changes to appliances, hot water systems or on-site generation do not directly improve the NatHERS thermal star rating, although they may influence a separate Whole of Home result. In NSW, the applicable requirements may also operate alongside BASIX.
In simple terms: NatHERS models the thermal performance of the dwelling design and building envelope. Whole of Home considers fixed appliances and energy systems beyond the thermal star rating. For building-envelope improvements, see how to improve a NatHERS rating.
Project Requirements
A NatHERS assessment is commonly needed when a new residential project must demonstrate the thermal performance of its dwelling design as part of an applicable energy-efficiency or approval pathway. This may apply to new houses, townhouses, dual occupancies, apartments, multi-dwelling developments and certain alteration or addition projects.
The exact requirement depends on the project location, building classification, scope of works, approval pathway and documentation stage. In NSW, a NatHERS assessment may operate alongside BASIX. In other states and territories, the NatHERS rating and certificate may connect more directly with building approval or NCC energy-efficiency documentation. The assessment can usually begin once the relevant plans and specifications are available.
Detached houses commonly require thermal modelling and a NatHERS star rating as part of the applicable residential approval or energy-efficiency pathway. The required outcome may include a 7 Star NatHERS benchmark.
Attached and semi-attached dwellings may require separate thermal modelling because orientation, exposure, glazing, shading and shared construction can vary between individual dwellings.
NatHERS results can differ between apartments in the same building due to level, orientation, glazing, shading, adjoining spaces and external exposure. The assessment process may therefore include modelling multiple individual dwellings.
Certain substantial alterations and additions may require thermal performance or residential energy-efficiency documentation, depending on their scope, location and approval pathway. Read more about whether renovations can require NatHERS.
Project note: Not sure whether NatHERS applies to your residential project? Send your plans for NatHERS review and Certified Energy can review the project type, approval context and information available for thermal assessment.
Project Documentation
A NatHERS assessment relies on clear residential project documentation. The assessor needs enough information to model the dwelling design accurately, including its layout, orientation, construction type, insulation, glazing, shading and other relevant building-envelope inputs. For a focused overview, see our guide to what information is needed for a NatHERS assessment.
The required information can vary depending on the project stage and applicable assessment pathway. Early plans can often be reviewed to identify thermal performance risks, but final modelling and certification usually require more complete architectural and specification information. See how this fits into the broader NatHERS assessment process.
Floor plans, elevations, sections, site plan and orientation are usually needed to understand the dwelling layout, external exposure and relationship to the site. Orientation can strongly influence glazing exposure, solar gain and the calculated rating.
Window and door schedules, glazing types, frame details and opening sizes can have a major influence on the NatHERS thermal model. Learn more about how window design affects NatHERS ratings.
Wall, roof, ceiling and floor construction details help define the thermal properties of the dwelling fabric. See why building fabric matters.
Insulation specifications are needed for roofs, ceilings, walls, floors and other relevant building-envelope elements. Read more about how insulation affects NatHERS ratings.
Eaves, awnings, balconies, pergolas, nearby buildings and other relevant shading elements can affect solar exposure within the thermal model. See how shading and solar heat gain influence NatHERS performance.
The project address, dwelling type, approval stage and applicable pathway help establish the correct climate data, modelling scope and certification requirements. For NSW projects, this may include relevant BASIX context.
Project note: You do not need to have every construction detail resolved before requesting an initial review. Send your plans for NatHERS review and Certified Energy can identify the information still needed for thermal modelling and certification.
Assessment Process
A NatHERS assessment usually begins with a review of the project documentation. The assessor uses the plans and specifications to model the dwelling design, calculate its heating and cooling loads and produce a thermal star rating. The result can then be reviewed against the applicable project requirements. See also what information is needed for a NatHERS assessment.
The assessor reviews the plans, project address, dwelling type, orientation, construction details and applicable approval context. For relevant NSW projects, this may include BASIX information.
The dwelling design is modelled using NatHERS rating tools and the relevant assessment inputs, including layout, construction, insulation, glazing, shading, ventilation and air-leakage assumptions, and climate data.
The thermal model calculates the dwelling’s heating and cooling loads and produces a NatHERS star rating. The result is then checked against the thermal performance outcome that applies to the project.
If the dwelling does not achieve the required rating, the assessor can identify the building-envelope and design factors affecting the result, such as glazing, insulation, shading or construction choices. Learn more about how to improve a NatHERS rating during design.
Once the dwelling achieves the applicable rating and the project information is complete, the NatHERS certificate and supporting assessment documentation can be prepared. These outputs can support the project’s residential energy-efficiency pathway.
In simple terms: NatHERS starts with the plans, moves through accredited thermal modelling and produces a star rating and supporting assessment documentation. If you are ready to check a project, send your plans for NatHERS review.
Design Factors
A NatHERS rating is shaped by how the dwelling’s design responds to its climate. The assessment does not consider one product or material in isolation. It models how orientation, glazing, insulation, shading, ventilation and air-leakage assumptions, construction and thermal mass work together within the dwelling design and building fabric.
This is why two dwellings with similar floor areas can receive different NatHERS ratings. A design with well-placed glazing, appropriate shading and suitable insulation may produce very different heating and cooling loads from a dwelling with poor orientation, exposed glazing or construction details that do not respond effectively to the local climate. For practical design-stage context, see how to improve a NatHERS rating during design.
The orientation of living areas, bedrooms and glazing can influence solar gain, heat loss and the calculated heating and cooling loads. Read more about why orientation matters for NatHERS.
Window size, frame type, glass performance and placement can have a strong effect on the dwelling’s calculated heating and cooling loads. See how window design affects NatHERS ratings.
Eaves, awnings, balconies, screens and nearby structures can alter solar exposure and heat gain within the NatHERS thermal model. See shading and solar heat gain explained.
Roof, ceiling, wall and floor insulation help limit unwanted heat transfer through the building envelope. Learn more about how insulation affects NatHERS ratings.
Lightweight and heavyweight construction can produce different thermal results depending on the local climate, orientation, insulation and thermal mass. This forms part of the broader building fabric response.
Openings, air-movement opportunities and ventilation assumptions can influence the modelled response to warmer conditions. Air leakage and ventilation assumptions can also affect the NatHERS thermal result.
In simple terms: NatHERS performance is rarely determined by one isolated product or specification. It reflects how the complete dwelling design and building envelope respond to the local climate. This is why early design review can make the assessment process smoother.
Rating Challenges
Some residential projects struggle to achieve the required NatHERS rating because thermal performance is considered too late in the design process. By the time the plans are ready for approval, key decisions about orientation, glazing, roof form, shading and construction may already be difficult to change. For many current new-home projects, the applicable outcome may include a 7 Star NatHERS rating.
Common issues include large areas of unshaded glazing, poor solar orientation, limited beneficial winter sun, excessive summer heat gain, insufficient insulation, roof colours that increase heat gain in warmer climates, complex building forms and window specifications that do not suit the project’s climate or exposure.
Apartments and attached dwellings can also present rating challenges because individual dwellings may have different orientations, levels, shared boundaries, glazing areas and external exposure. One dwelling may therefore produce different heating and cooling loads from another dwelling in the same development, which is why the NatHERS assessment process may need to consider individual dwelling performance.
If a dwelling design is falling short of the required NatHERS rating, the solution is not always one major specification change. The result may be improved through a coordinated combination of glazing, insulation, shading, roof colour, construction details and other building-envelope adjustments. For practical guidance, see how to improve a NatHERS rating during design.
Project note: If your dwelling design is not achieving the required rating, send your plans for NatHERS review and Certified Energy can help identify which building-envelope, design or specification inputs are affecting the thermal result.
Early Review
Early NatHERS advice can help project teams understand the likely thermal performance of a dwelling design before it becomes difficult to change. This is particularly useful where a project must achieve an applicable NatHERS rating, which may include a 7 Star NatHERS benchmark for many current new-home projects.
A preliminary review can identify whether the modelled result is likely to be affected by glazing, orientation, shading, insulation, roof colour, construction type or ventilation and air-leakage assumptions. These factors are often easier to coordinate while the plans and specifications are still being developed.
For architects and building designers, early advice can provide clearer feedback on how design decisions affect heating and cooling loads. For builders and developers, it can reduce the risk of late building-envelope or specification changes. For homeowners, it can clarify what may need to change before the NatHERS assessment is finalised. See our guide to how to improve a NatHERS rating during design.
Early review does not replace the final NatHERS assessment or certificate. It provides an opportunity to identify thermal performance risks, test suitable building-envelope responses and understand the information that will be needed as the project moves through the NatHERS assessment process.
In simple terms: Early NatHERS advice helps identify building-envelope and thermal performance issues before they become harder, slower or more expensive to resolve. If you already have plans, send your plans for NatHERS review.
Project Support
Certified Energy supports architects, building designers, builders, developers and homeowners with NatHERS assessments, accredited thermal modelling, design-stage review and NatHERS certification for new residential projects.
The role is not limited to producing a star rating. A well-managed NatHERS assessment can help explain how the dwelling design is performing, identify the building-envelope inputs affecting the heating and cooling loads and confirm what is needed before the assessment can be finalised.
For relevant NSW projects, Certified Energy can clarify how the NatHERS thermal assessment connects with BASIX. Where fixed appliances and household energy systems are also being considered, the distinction between the thermal star rating and Whole of Home can also be explained.
If the property is an established dwelling rather than a new-home design or residential approval project, the more relevant service may be an existing Home Energy Rating. That assessment focuses on the energy performance and improvement opportunities of an existing home rather than new-home NatHERS compliance.
Where a new dwelling is still in design, early NatHERS review can help identify whether glazing, insulation, shading, orientation or construction details are likely to affect the modelled rating. See how early NatHERS advice can help before the plans and specifications are finalised.
Project note: Need to confirm the NatHERS scope for a new residential project? Send your plans for NatHERS review and Certified Energy can assess the dwelling type, available documentation and thermal modelling requirements. You can also check what information is usually needed before submitting project documents.
Certificates & Reports
The terms NatHERS assessment, NatHERS report and NatHERS certificate are often used together, but they describe different stages or outputs of the same thermal energy-rating process.
A NatHERS assessment is the thermal modelling process. The assessor reviews the project documentation, enters the relevant dwelling design, building-envelope and construction inputs into accredited software, and calculates the dwelling’s thermal star rating.
The certificate and supporting assessment documentation record the completed NatHERS result and relevant project information. These outputs may be used within the project’s approval or residential energy-efficiency documentation. The exact documentation required can depend on the project location, building type, approval pathway and, for relevant NSW projects, its relationship with BASIX.
The accredited thermal modelling process used to calculate the dwelling’s heating and cooling loads and NatHERS thermal star rating.
Supporting assessment documentation that records relevant modelling inputs, assumptions and rating information from the assessment process.
The formal NatHERS output confirming the assessed dwelling design and rating result for use within the applicable approval or energy-efficiency pathway.
In simple terms: The assessment is the thermal modelling work. The certificate and supporting documentation record the assessed dwelling design and NatHERS rating outcome. If you need formal NatHERS documentation for a project, send your plans for NatHERS review.
Timeframes
The timeframe for a NatHERS assessment depends on the project type, the quality and completeness of the project documentation, the number of dwellings and whether design changes are needed to achieve the required NatHERS star rating.
A straightforward new house with clear plans, elevations, sections, glazing details and construction specifications is generally simpler to model than a complex townhouse development, apartment project or substantial alteration and addition with incomplete information. See what information is usually needed for a NatHERS assessment.
The main timing issue is often not the initial thermal modelling itself, but the coordination required when information is missing, modelling assumptions need to be confirmed or the first result does not achieve the required NatHERS outcome. Where revisions are needed, the dwelling design or specifications may need to be updated and reassessed before the certificate and supporting documentation can be finalised.
The overall project timeframe can also depend on when the NatHERS assessment is required within the applicable approval and documentation pathway. For relevant NSW projects, this may include coordination with BASIX, but the NatHERS assessment itself remains focused on completing the dwelling thermal model and rating documentation.
Project note: Clear plans, specifications and glazing information usually make the NatHERS process smoother and reduce the need for follow-up clarification. Send your plans for review to confirm what is still needed before thermal modelling and certification.
Cost Factors
The cost of a NatHERS assessment depends on the project type, number of dwellings, documentation quality, design complexity and whether modelling revisions or design review are needed to achieve the required NatHERS star rating.
A single detached house is generally simpler to assess than a townhouse development, apartment building or substantial alteration and addition. Projects with repeated dwelling types may also require a different modelling scope from developments where individual dwellings have unique layouts, orientations, glazing arrangements or exposure conditions.
The assessment cost can also be influenced by the stage of design, the completeness of the building-envelope specifications and the amount of coordination required before certification. For relevant NSW projects, the NatHERS scope may also need to align with BASIX documentation, while the thermal modelling itself remains focused on the dwelling design and star-rating result.
For an accurate quote, Certified Energy generally needs the project address, architectural plans, elevations, sections, window schedule if available and a short description of the project stage. These details help establish the number of dwelling models required, the likely assessment process and whether preliminary thermal performance review may be needed.
Project note: The most accurate way to confirm pricing is to send your plans for NatHERS review so the dwelling type, documentation, thermal modelling scope and certification requirements can be reviewed properly.
Rating Review
If a dwelling design does not achieve the required NatHERS rating, the thermal model usually needs to be reviewed before the final certificate and supporting documentation can be completed. For many current new-home projects, the applicable outcome may include a 7 Star NatHERS rating.
The appropriate response depends on which building-envelope or design inputs are affecting the result. In some projects, the issue may be large areas of unshaded glazing. In others, it may relate to insulation levels, roof colour, orientation, construction type, ventilation and air-leakage assumptions, shading or differences between individual dwellings within a townhouse or apartment development. See the common reasons a NatHERS rating can fall short.
Potential adjustments may include improved glazing specifications, additional insulation, revised shading, lighter roof colours, changes to window sizes or other building-envelope and specification updates. The most appropriate response should be guided by the calculated heating and cooling loads and the specific inputs affecting the modelled result.
After suitable changes have been agreed, the dwelling design can be modelled again to confirm whether the required rating has been achieved. This review-and-adjustment stage forms part of the broader NatHERS assessment process and is generally easier to manage before the plans and specifications are finalised.
In simple terms: If the rating falls short, the dwelling design usually needs targeted building-envelope or thermal performance adjustments followed by further modelling. See how early NatHERS advice can help, or send your plans for NatHERS review if you need help identifying what is affecting the result.
Assessors & Software
A NatHERS assessment used for formal rating and certification should be completed by an appropriately qualified assessor using NatHERS-accredited software. The assessor uses the project documentation to create a thermal model of the dwelling design, calculate its heating and cooling loads and produce the NatHERS star rating.
The accuracy of the model depends on the plans, specifications and construction information provided. Window details, insulation levels, wall, roof and floor build-ups, shading, orientation and applicable climate data must be represented correctly. These inputs form part of the broader design factors that affect a NatHERS rating.
A NatHERS assessment is not simply an automated software result. The assessor must interpret the project documentation, apply the relevant modelling protocols, identify inconsistencies or missing information and review the thermal result in the context of the dwelling design. See how the NatHERS assessment process works.
Certified Energy supports this process through project-document review, accredited thermal modelling, rating analysis and preparation of NatHERS assessment documentation. For relevant NSW projects, the team can also clarify how the NatHERS result connects with BASIX, while keeping the thermal assessment focused on the dwelling design and building envelope.
In simple terms: A NatHERS assessor converts the project documentation into an accredited thermal model, reviews the calculated heating and cooling performance and prepares the relevant rating documentation. If you need an assessment, send your plans for NatHERS review.
New Homes & Existing Homes
This NatHERS Knowledge Hub is focused on thermal performance modelling, star ratings and certification for proposed new dwellings. It is most relevant to new houses, townhouses, apartments, dual occupancies and certain substantial alteration or addition projects where a NatHERS assessment forms part of the applicable approval or energy-efficiency pathway.
Existing home assessments are different. They assess an established dwelling rather than a proposed new-home design and may identify how its existing building fabric, energy performance and potential retrofit opportunities could be improved.
If the property is an existing dwelling rather than a proposed new home or residential approval project, the more relevant resource is the Home Energy Rating Knowledge Hub. That pathway focuses on assessing an already built home and identifying possible energy-performance and retrofit improvements.
Used to model and rate the expected thermal performance of a proposed dwelling design before construction. This is the main focus of this NatHERS Knowledge Hub.
Used to assess the energy performance of an established dwelling and identify possible improvement or retrofit opportunities. See Home Energy Ratings for existing homes.
In simple terms: NatHERS on this page is about modelling and rating proposed new dwelling designs. Existing homes belong within a separate assessment and retrofit-improvement pathway. If you are working on a new residential project, send your plans for NatHERS review.
Frequently Asked Questions
A NatHERS assessment uses accredited thermal modelling software to assess the expected thermal performance of a dwelling design. It calculates the heating and cooling loads and produces a star rating from 0 to 10 stars. See what NatHERS means for the broader explanation.
No. NatHERS is the thermal modelling and rating framework. A 7 Star Energy Rating is a thermal performance outcome produced within that framework, not a separate assessment system. For more detail, see what 7 Star NatHERS means or our guide to 7 Star Energy Ratings.
6 Star remains relevant as a former residential benchmark and for older projects, historical context and comparison with newer requirements. For many current new-home projects, 7 Star is the more relevant benchmark, subject to the applicable jurisdiction and approval pathway. See 6 Star vs 7 Star NatHERS or read our guide to 6 Star vs 7 Star NatHERS ratings.
The requirement depends on the project type, scope of works and approval pathway. BASIX is the broader NSW planning and sustainability framework, while NatHERS is the thermal modelling and star-rating pathway that may be used to demonstrate dwelling thermal performance within the applicable BASIX process. Read more in NatHERS and BASIX, our article on BASIX and NatHERS in NSW or our full BASIX Knowledge Hub.
No. The NatHERS thermal star rating reflects the calculated heating and cooling loads of the dwelling design and building envelope. Whole of Home considers fixed appliances and household energy systems beyond that thermal result, including relevant heating and cooling equipment, hot water, lighting and on-site energy generation. See NatHERS and Whole of Home, read more about how NatHERS and Whole of Home are connected or visit the full Whole of Home Knowledge Hub.
A NatHERS assessment usually requires architectural plans, elevations, sections, site and orientation information, window schedules, glazing details, construction build-ups and insulation specifications. The information must be detailed enough for the assessor to model the dwelling design and building envelope accurately. See what information is needed for a NatHERS assessment or read our guide to what documents are needed for a NatHERS assessment.
Timing depends on the project type, modelling complexity, number of dwellings, documentation quality and whether design or specification changes are needed to achieve the required rating. Clear plans, window schedules and construction details usually reduce follow-up clarification and make the assessment process smoother. See how long a NatHERS assessment takes or read our article on NatHERS assessment timeframes.
Cost depends on the project type, number of dwelling models, design complexity, documentation quality and whether additional thermal modelling or design revisions are required. Certified Energy can provide a project-specific quote after reviewing the plans and confirming the assessment scope. See NatHERS assessment cost factors or read more about how much a NatHERS assessment costs.
If the dwelling design does not achieve the required rating, the thermal model is reviewed to identify which building-envelope or design inputs are affecting the result. Adjustments may involve glazing, insulation, shading, roof colour, window sizes, construction details or ventilation and air-leakage assumptions. The revised design can then be modelled again before the certificate and supporting documentation are finalised. See what happens if the design does not reach 7 Star or read our guide to what happens if a home fails NatHERS.
This page focuses on NatHERS thermal modelling, star ratings and certification for proposed new dwellings and certain residential approval projects. An established dwelling is generally better suited to a separate Home Energy Rating or Residential Efficiency Scorecard pathway, where the focus is on existing energy performance and possible improvement opportunities. See new homes vs existing home ratings or read about NatHERS existing homes vs new home NatHERS assessments.
Yes. You can send your plans for NatHERS review and Certified Energy can assess the dwelling type, available documentation, thermal modelling scope and information required to begin the assessment. Where relevant, the team can also identify how the NatHERS result relates to the applicable approval context. You can also check what information is usually needed before submitting your project documents.
Related Knowledge
NatHERS is the thermal modelling and star-rating pathway for proposed dwellings. These related guides explain connected NSW requirements, broader household energy systems, rating benchmarks and separate assessment pathways for existing homes.
Project Review
Send the available plans, elevations, sections, glazing information and project details for an initial review. Certified Energy can assess the dwelling type, available documentation and likely thermal modelling requirements for the NatHERS assessment.
Early review can identify missing modelling inputs, clarify the likely assessment and certification process, and highlight building-envelope or thermal performance issues before the design progresses further. For relevant projects, the relationship with BASIX or Whole of Home documentation can also be clarified without changing the primary NatHERS assessment focus.
Last reviewed: June 2026. This page is maintained by Certified Energy as part of its NatHERS Knowledge Hub.
