Residential Energy Performance
Understand how heating and cooling, hot water, lighting, cooking, appliances, solar PV and battery storage contribute to the modelled energy performance of a new home.
For homeowners, architects, building designers and builders seeking to understand how the Whole of Home score works alongside the NatHERS thermal star rating and relevant residential energy requirements.
Explore Whole of HomeIn Brief
A NatHERS Whole of Home rating assesses the modelled energy performance of the major systems and energy uses within a new home. It complements the thermal star rating by looking beyond the building shell to consider how energy is used, generated and stored across the dwelling.
The thermal star rating assesses the heating and cooling load created by the home’s design, orientation, glazing, insulation, shading and construction. The Whole of Home rating considers additional energy uses including heating and cooling equipment, hot water, lighting, cooking and plug loads, as well as pool or spa equipment where applicable.
Onsite solar generation and battery storage are also included in the calculation. The result is expressed as a score out of 100 and may form part of the NatHERS pathway used to demonstrate compliance with applicable residential energy requirements.
Heating and cooling equipment, hot water, lighting, cooking and plug loads, pools and spas, solar PV and battery storage.
It is a complementary NatHERS rating that works alongside the thermal star rating rather than operating as a separate assessment framework.
A modelled Whole of Home score out of 100 showing the combined effect of household energy use, onsite generation and storage.
Knowledge Navigation
Understand what the Whole of Home rating assesses, how the score works, when it may be required and how household systems, solar generation and battery storage influence the result.
Rating Foundations
Score and Requirements
Compliance Context
Project Inputs
Assessment Outcome
Rating Foundations
A NatHERS Whole of Home rating provides a modelled assessment of the energy used, generated and stored across a new home. It complements the thermal star rating by assessing the major household systems that operate within the dwelling.
A standard NatHERS thermal star rating assesses the heating and cooling load created by the design and construction of the building shell. The Whole of Home rating extends the assessment to include the energy performance of specified household equipment and onsite energy systems.
This includes heating and cooling equipment, hot-water systems, lighting, cooking and plug-in appliances, pool and spa equipment, solar photovoltaic systems and battery storage. These inputs are modelled using consistent assessment assumptions so that proposed homes can be compared on a common basis.
The result is expressed as a separate rating out of 100. It may be used alongside the thermal star rating to demonstrate the annual energy-use component of applicable residential energy requirements, subject to the pathway and jurisdiction applying to the project.
At a Glance
Modelled household energy use, onsite generation and energy storage.
A separate Whole of Home rating expressed on a scale out of 100.
Used together with the NatHERS thermal star rating to provide two complementary views of residential energy performance.
Two Complementary Ratings
A NatHERS assessment can provide two complementary ratings: a thermal star rating for the building shell and a Whole of Home rating for the major energy systems operating within the dwelling.
Building Shell
The thermal star rating assesses how the design and construction of the home influence the energy needed to maintain comfortable indoor temperatures.
It considers factors such as orientation, floor plan, glazing, insulation, shading, construction materials, ventilation and local climate. The result is expressed as a star rating out of 10.
Household Systems
The Whole of Home rating assesses the modelled energy performance of the equipment and energy systems specified for the dwelling.
It includes heating and cooling equipment, hot water, lighting, cooking and plug loads, pool and spa equipment where relevant, solar PV and battery storage. The result is expressed as a score out of 100.
A home can have a strong thermal star rating but still receive a weaker Whole of Home result if inefficient equipment or limited onsite generation is specified. Conversely, efficient appliances and a large solar system do not remove the need for a well-designed thermal shell.
Together, the two ratings provide a more complete assessment of the proposed home: one focuses on the building fabric and thermal load, while the other focuses on household energy use, generation and storage. Learn more about the broader NatHERS assessment framework.
Assessment Scope
The Whole of Home assessment models the major energy uses, onsite generation and energy storage associated with the proposed dwelling. The inputs reflect the systems specified for the project and standardised assumptions used by NatHERS.
Indoor Comfort Systems
The assessment considers the type and efficiency of the heating and cooling equipment specified for the home, together with the modelled thermal loads produced by the building design.
Water Heating
The selected hot-water system contributes to the Whole of Home result. The calculation considers the system type, energy source and relevant performance characteristics.
Household Energy Uses
Lighting, cooking and common household plug loads are included using NatHERS calculation assumptions. These loads help represent the wider operational energy demand of the dwelling.
Additional Equipment
Where a pool or spa forms part of the project, relevant pumps, heating equipment and associated energy demand may be included in the assessment.
Onsite Generation
A proposed solar PV system can offset modelled household energy demand. System capacity, orientation and other relevant project inputs contribute to its calculated effect on the rating.
Energy Storage
Where battery storage is specified, the assessment can account for how stored solar energy contributes to the modelled performance of the home.
The Whole of Home rating uses standardised occupancy and energy-use assumptions so that homes can be assessed consistently. Actual household consumption and energy costs may vary according to occupant behaviour, weather conditions, equipment use, tariffs and future changes to the dwelling.
Rating Scale
The Whole of Home result is expressed as a rating out of 100. A higher score indicates a lower modelled energy value after household energy use, onsite solar generation and battery storage have been considered.
The rating is calculated from the modelled energy performance of the dwelling’s heating and cooling equipment, hot-water system, lighting, cooking and plug loads, together with pool or spa equipment where applicable. The calculation then accounts for energy generated by solar PV and the contribution of battery storage.
The result is not a percentage and should not be read as a direct prediction of energy consumption or household bills. It is a comparative rating produced using NatHERS calculation methods, standardised occupancy assumptions and consistent operating conditions.
A higher score generally reflects a combination of lower modelled energy demand, more efficient household systems and greater contribution from onsite renewable energy. The balance between these elements will vary from project to project.
Reading the Result
Below 100
The home has a positive modelled energy value after its household energy use, solar generation and storage have been considered.
100
A score of 100 represents a net zero energy value home under the NatHERS rating method.
Above 100
Ratings above 100 are possible where the modelled benefit of onsite energy generation exceeds the assessed energy value of the home.
The Whole of Home score can be influenced by the thermal loads produced by the building design, the type and efficiency of the specified equipment, the energy source used by household systems, the presence of pools or spas and the size and performance of any proposed solar PV or battery system.
A project should therefore be reviewed as an integrated assessment rather than relying on one isolated improvement. Solar generation may strengthen the result, but it does not replace the need for an appropriate thermal shell and efficient household systems.
Project Requirements
A Whole of Home rating is most commonly prepared for new residential projects where the applicable energy-efficiency pathway requires an assessment of annual household energy use.
NCC 2022 introduced a whole-of-home annual energy-use requirement for new residential buildings. A NatHERS Whole of Home rating can be used to demonstrate this part of the residential energy provisions where the NatHERS pathway is available and adopted for the project.
Whether a rating is required depends on the building classification, project location, approval pathway and the residential energy provisions adopted by the relevant state or territory. Jurisdictional variations and transition arrangements may affect the assessment required.
The requirement should therefore be confirmed before the assessment begins rather than assuming that the same Whole of Home threshold or compliance pathway applies to every Australian project.
Common Project Contexts
A rating may form part of the NatHERS pathway used for a new Class 1 dwelling under the applicable residential energy requirements.
Whole of Home requirements can also apply to new apartment developments, subject to the assessment method and jurisdictional provisions.
A project team may also use the rating to compare system selections or pursue a stronger performance outcome beyond the minimum requirement.
Projects in New South Wales may also need to address BASIX requirements, while other jurisdictions may apply different NCC adoption arrangements. Existing homes follow a separate Home Energy Rating pathway and should not be treated as new-home Whole of Home assessments.
NCC 2022 Context
NCC 2022 introduced two related residential energy-performance considerations: the thermal performance of the building and an annual energy-use requirement for the home’s major energy systems.
Requirement One
The thermal-performance provisions address how effectively the building shell responds to the local climate. They consider the influence of orientation, glazing, insulation, shading, construction and the overall dwelling design.
Where a NatHERS assessment pathway is used, this part of the project is represented by the thermal star rating out of 10.
Requirement Two
The annual energy-use provisions consider the energy associated with major household systems, including space conditioning, hot water, lighting, pools and spas, together with the contribution of onsite renewable-energy generation.
A NatHERS Whole of Home rating can be used to demonstrate this component where the energy-rating pathway applies to the project.
The NatHERS Whole of Home rating is not the only method available under the NCC. Depending on the building classification and selected compliance pathway, a project may use an energy-rating method, the applicable Residential Deemed-to-Satisfy provisions, a Verification Method or another appropriately developed Performance Solution.
The thermal and annual energy-use requirements should be considered together. Meeting a Whole of Home target does not remove the need to satisfy the applicable thermal-performance requirement, and a compliant thermal star rating does not by itself demonstrate compliance with the annual energy-use provisions.
Jurisdictional Adoption
States and territories can adopt the NCC with different commencement dates, variations and transitional arrangements.
The required pathway and rating threshold should therefore be confirmed against the current rules applying to the project rather than assumed from the national framework alone.
New South Wales Context
New residential projects in New South Wales generally address household energy, thermal performance and water efficiency through BASIX rather than through a separate NatHERS Whole of Home rating.
BASIX is a New South Wales planning assessment that applies to new residential development and certain alterations, additions, pools and spas. It assesses water efficiency, energy performance and thermal performance through the NSW Planning Portal.
For NSW projects, the BASIX energy section considers relevant household systems such as heating and cooling, hot water, lighting, cooking, appliances and onsite energy generation. This creates some technical overlap with the inputs considered by NatHERS Whole of Home, but the two are not interchangeable certificates.
A NatHERS thermal assessment may still be used to support the thermal-performance component of a BASIX submission. The resulting NatHERS star rating can therefore sit within the NSW BASIX process without requiring the project to follow the separate national Whole of Home rating pathway.
Key Distinctions
A NSW planning and sustainability assessment covering water, energy and thermal-performance requirements.
A thermal star rating that may be used to demonstrate the thermal-performance component of the BASIX assessment.
A separate NatHERS rating used in jurisdictions and project pathways that adopt the national annual energy-use assessment method.
The project will usually need to follow the NSW BASIX pathway. The required thermal assessment, energy inputs and supporting documents should be identified early so they can be coordinated with the design.
Explore the BASIX Knowledge HubNCC Compliance Pathways
NatHERS Whole of Home and the prescriptive Residential DTS provisions can both support residential energy compliance, but they demonstrate performance through different assessment methods.
Modelled Assessment
The NatHERS pathway uses accredited software to model the proposed dwelling. It can provide a thermal star rating for the building shell and a separate Whole of Home rating for household energy use, onsite generation and battery storage.
This pathway allows the interaction between orientation, glazing, insulation, construction, thermal loads and specified household systems to be assessed within a project-specific model.
Prescriptive Assessment
The elemental pathway follows the applicable prescriptive provisions for building fabric, glazing, sealing, ceiling fans, services and whole-of-home energy usage.
Rather than producing a NatHERS rating, the design is checked against the relevant construction and services requirements prescribed for the project.
Under the NCC, both the NatHERS software pathway and the prescriptive elemental provisions can form part of a Deemed-to-Satisfy Solution. The distinction is therefore not simply NatHERS versus DTS, but between different methods available for demonstrating the residential energy Performance Requirements.
Within the Certified Energy Knowledge Hub, Residential DTS is used primarily to describe the elemental or prescriptive route. The NatHERS pathway is discussed separately because it relies on project-specific energy modelling and produces formal ratings.
The most suitable route depends on the building type, design, jurisdiction, documentation available and the flexibility required by the project team.
Pathway Boundary
The prescriptive elemental pathway can address the NCC whole-of-home energy-use requirement without producing a NatHERS Whole of Home score.
Where a formal rating out of 100 is required, the project must follow the applicable NatHERS Whole of Home assessment method.
Alternative Assessment Pathway
VURB and NatHERS Whole of Home address different parts of residential energy performance. VURB evaluates the proposed building against a reference building, while Whole of Home assesses the energy performance of household systems, generation and storage.
Reference-Building Verification
Verification Using a Reference Building compares the modelled performance of a proposed dwelling with a compliant reference building. It can provide an alternative way to demonstrate the applicable thermal-performance requirement where the project does not follow the standard NatHERS thermal-rating route.
The method is centred on the building design and its thermal response. It does not produce a NatHERS thermal star rating or a Whole of Home score out of 100.
Household Energy Assessment
The Whole of Home assessment models energy used by heating and cooling equipment, hot water, lighting, cooking, plug loads and other applicable household systems.
It also accounts for solar PV and battery storage and expresses the result as a separate rating out of 100 under the NatHERS assessment method.
Where VURB is used to address the thermal performance of the proposed dwelling, the project may still need to demonstrate compliance with the separate annual energy-use provisions. The applicable method should be identified as part of the overall residential compliance strategy.
A project should not assume that a successful reference-building comparison automatically satisfies the household energy component. Heating and cooling equipment, hot water, lighting, pools, spas and onsite generation may need to be documented and assessed through the relevant complementary pathway.
Learn more about when VURB may provide an alternative residential compliance pathway.
Assessment Boundary
VURB produces a reference-building verification outcome for the applicable building-performance requirement.
NatHERS Whole of Home produces a formal household energy rating out of 100. The two outcomes should not be described as equivalent.
Project Information
A reliable Whole of Home rating requires coordinated information about the dwelling design, proposed household systems and any onsite energy generation or storage included in the project.
Dwelling Design
Current floor plans, elevations, sections, orientation and site information are required to establish the dwelling geometry and connect the assessment with the underlying thermal model.
Glazing, insulation, construction systems and shading information may also be required as part of the associated NatHERS assessment.
Space Conditioning
The assessor needs to understand the proposed heating and cooling strategy, including the equipment type, areas served and relevant efficiency information.
Where final products have not been selected, suitable provisional specifications may be used and updated as the design develops.
Household Services
Information is required about the proposed hot-water system, cooking energy source and any project-specific lighting inputs relevant to the assessment.
The system type, energy source, capacity and available performance data help establish the appropriate modelling inputs.
Onsite Energy
Where solar PV is proposed, the system capacity, panel orientation and available design information should be provided.
Battery capacity and relevant storage details are also required where battery storage is intended to contribute to the Whole of Home result.
Additional Loads
Any proposed pool or spa should be identified early so the relevant pumps, heating systems and associated energy demand can be included where applicable.
Omitting these elements from the initial documentation can lead to later revisions when the assessment is finalised.
Project Context
The project address, building classification and proposed approval pathway help determine the assessment requirements applying to the dwelling.
This is particularly important where jurisdictional variations, apartment averaging provisions or alternative compliance methods may apply.
Not every equipment model needs to be finalised before preliminary assessment begins. Early modelling can use documented design assumptions to identify whether the proposed combination of building fabric, household systems and onsite generation is likely to achieve the required outcome.
As selections are confirmed, the model should be updated so the final rating and certificate accurately reflect the project documentation intended for approval and construction.
Rating Influences
The Whole of Home result is shaped by the interaction between the dwelling’s thermal performance, the efficiency of its household systems and the contribution of onsite solar generation and battery storage.
A Whole of Home assessment is most useful when it is coordinated with the design rather than treated as a final equipment check. Decisions about glazing, insulation, shading and orientation influence the heating and cooling loads that household systems must meet.
The efficiency and energy source of the selected heating, cooling and hot-water systems can then strengthen or weaken the result. Cooking, lighting, pools and spas may also contribute to the modelled household energy demand, while solar PV and battery storage can improve the assessed energy balance.
Because the thermal star rating and Whole of Home rating are connected, changes to the building shell may affect both outcomes. Early coordination with the broader NatHERS assessment can reduce the risk of late design or specification changes.
Four Connected Influences
The building design influences how much heating and cooling energy is modelled for the dwelling.
The type and performance of heating, cooling and hot-water equipment affect modelled energy use.
The fuels and energy sources used for major household systems contribute to the rating calculation.
Solar PV and battery storage can offset modelled energy demand and improve the Whole of Home result.
Adding more solar may improve the rating, but it does not correct every weakness in the dwelling design or household system specification. Similarly, highly efficient equipment cannot fully compensate for unnecessary heating and cooling loads created by the building shell.
The most reliable pathway is to coordinate thermal design, household systems and onsite energy from an early stage. This allows the project team to compare practical options while architectural and services decisions can still be adjusted.
Assessment Process
The assessment combines the dwelling’s thermal model with information about the proposed household systems, solar generation and battery storage. Early review allows the result to be coordinated with the design before documentation is finalised.
01
The first step is to confirm the project location, building classification, approval pathway and applicable residential energy provisions. This establishes whether a Whole of Home rating is required and identifies any jurisdictional variations that need to be addressed.
02
The assessor reviews the architectural documentation, construction specifications and the proposed heating, cooling, hot-water, cooking, lighting, solar and battery systems.
Providing the required assessment information together helps reduce assumptions and unnecessary revisions.
03
The dwelling is modelled using NatHERS-accredited software. The thermal assessment establishes the heating and cooling loads created by the building design, while the Whole of Home calculation assesses the specified household systems, onsite generation and energy storage.
These calculations produce the complementary thermal star rating and Whole of Home rating where both form part of the selected NatHERS assessment pathway.
04
Preliminary modelling shows whether the proposed dwelling and household systems are likely to achieve the required outcome. Where improvement is needed, the assessor can identify which design or specification inputs are influencing the result.
Possible responses may include refining the thermal design, improving equipment efficiency or reviewing the proposed solar and battery systems. Changes should be considered in the context of the complete assessment rather than as isolated substitutions.
05
Once the design and system selections are confirmed, the assessment is updated to match the documentation intended for approval and construction. The final result is recorded through the applicable NatHERS certificate or assessment documentation.
The plans and specifications should remain consistent with the assessed inputs. Material changes made after certification may require the model and supporting documentation to be reviewed again.
Completing preliminary modelling during design development gives the project team time to coordinate building fabric, services and onsite energy systems. When assessment is delayed until documentation is complete, the available responses may be more limited or require wider changes to the plans and specifications.
Assessment Outcome
The final NatHERS documentation records the assessed dwelling, its thermal star rating and, where a Whole of Home assessment has been completed, the separate rating for household energy use, onsite generation and storage.
The NatHERS certificate provides a formal record of the dwelling assessed through accredited software. It identifies the project and summarises the modelled results produced from the plans, construction details and household system information supplied to the assessor.
The thermal star rating and Whole of Home rating should be read as two complementary outcomes. The star rating describes the modelled thermal performance of the building shell, while the Whole of Home rating reflects the energy value associated with major household systems, solar PV and battery storage.
The certificate does not replace the architectural drawings, specifications or approval documentation. Those documents should remain consistent with the materials, glazing, insulation, appliances and onsite energy systems represented in the assessment.
Certificate Overview
The building shell’s modelled thermal performance, expressed as a rating out of 10.
The modelled energy value of household systems, onsite generation and storage, expressed as a rating out of 100.
Project information and key assessment details used to identify the dwelling represented by the results.
A summary of the household systems and renewable-energy inputs included in the Whole of Home calculation.
Before the assessment is relied upon for approval or construction, the project team should confirm that the dwelling address, floor plans, construction systems, glazing, insulation and major household energy systems align with the information used in the model.
Changes to heating and cooling equipment, hot-water systems, cooking energy, pool or spa equipment, solar PV or battery storage may alter the Whole of Home result. Material design changes should therefore be referred back to the assessor before the documentation is finalised.
For further context on the wider rating framework, explore the NatHERS Knowledge Hub or review how the Whole of Home assessment process works.
Reading the Outcome
The rating should be read as a modelled performance outcome for the assessed dwelling—not as a percentage, appliance-efficiency label or prediction of the future household energy bill.
The first question is whether the rating achieves the target applying to the project. The required outcome may depend on the building type, jurisdiction, approval pathway and any relevant state or territory variation.
The numeric score should then be reviewed together with the underlying assessment inputs. A result may reflect the efficiency of the specified heating, cooling and hot-water systems, the modelled household loads, the presence of a pool or spa and the contribution of solar PV or battery storage.
Understanding which inputs are driving the result is more useful than looking at the score in isolation. This allows the project team to determine whether any improvement should come from the building design, household systems, onsite generation or a combination of these elements.
What the Score Can Show
Whether the assessed dwelling achieves the Whole of Home target applying to the selected project pathway.
How the proposed heating, cooling, hot-water and other household systems contribute to the result.
The effect of solar PV and battery storage on the modelled energy value of the dwelling.
Which design or specification changes may provide a practical pathway to a stronger result.
A score of 80 does not mean the dwelling is 80 per cent efficient. The rating scale represents an energy-value outcome calculated under the NatHERS method.
Actual household consumption and costs will vary with occupant behaviour, tariffs, weather, equipment operation and future changes to the dwelling.
The thermal star rating and Whole of Home rating describe different aspects of the proposed dwelling and should be reviewed together.
The Whole of Home score is most meaningful when reviewed alongside the thermal star rating, assessed plans, system specifications and applicable compliance target.
Review how the Whole of Home score works or explore the wider NatHERS Knowledge Hub.
Performance Improvement
A stronger Whole of Home result usually comes from coordinating the thermal design, household systems and onsite energy strategy rather than relying on one isolated change.
The most appropriate improvement depends on the project. A dwelling with high heating and cooling loads may benefit from changes to glazing, insulation, shading or other parts of the thermal design. A dwelling with a sound building shell may instead require more efficient heating, cooling or hot-water equipment.
Solar PV and battery storage can improve the modelled energy balance, but they should be considered alongside the energy demand of the dwelling. Increasing generation may strengthen the score without addressing inefficient equipment or unnecessary thermal loads.
Preliminary modelling allows the assessor and project team to compare practical changes before the plans and specifications are finalised. This is generally more effective than waiting until the project requires a late compliance correction.
Improvement Priorities
Review the building design where heating and cooling demand is placing pressure on the result.
Compare the performance of proposed heating, cooling and hot-water systems.
Check the contribution of pools, spas and other relevant household energy uses.
Assess whether the proposed solar PV and battery systems are appropriately sized and represented.
Building Design
Orientation, glazing, insulation, shading, sealing and construction choices can reduce the heating and cooling loads carried into the Whole of Home calculation.
Space Conditioning
Efficient equipment, appropriate zoning and clear specification of the areas served can improve the modelled performance of the proposed systems.
Water Heating
The energy source, system type and performance of the selected hot-water equipment can have a meaningful effect on the rating.
Household Systems
Cooking energy, lighting assumptions and applicable household loads should be reviewed together rather than as disconnected specifications.
Onsite Generation
The proposed system capacity, orientation and available roof area can influence how much onsite generation contributes to the assessment.
Energy Storage
Where battery storage is proposed, its capacity and relationship with the solar system should be accurately represented in the model.
The objective should be a coordinated and buildable design that achieves the required Whole of Home outcome. Substitutions made only to increase the rating may create conflicts with architectural intent, services coordination, documentation or construction cost.
Review the relationship between design and system selections or explore how the wider NatHERS assessment addresses the thermal performance of the dwelling.
Assessment Boundary
The NatHERS Whole of Home rating described on this page is primarily associated with the assessment of new residential projects. Existing homes follow a separate Home Energy Rating pathway.
New Residential Projects
For a proposed dwelling, the assessment is completed from architectural documentation, construction specifications and the household energy systems intended for the project.
The result works alongside the NatHERS thermal star rating and may support the applicable new-home energy-compliance pathway.
Existing Residential Buildings
An existing home is assessed through a different process that reflects the building and systems already in place. This may involve an onsite assessment, evidence of existing construction and review of current household equipment.
The outcome may also help the homeowner understand potential upgrade priorities, which sits outside the purpose of a new-home Whole of Home compliance assessment.
Both pathways can consider the interaction between the building shell, household systems and onsite energy. The difference lies in the project context, assessment process and intended outcome.
A new-home Whole of Home assessment evaluates a proposed design and specification before construction. A Home Energy Rating assesses an existing dwelling and can provide a clearer basis for understanding its present performance and possible improvements.
Existing-home retrofit planning, staged upgrades and recommendations about insulation, glazing, draught sealing or appliance replacement belong within the Home Energy Rating Knowledge Hub.
Choose the Right Pathway
Proposed dwelling: assess the design, thermal model and specified household systems through the applicable new-home pathway.
Existing dwelling: use the Home Energy Rating pathway where an assessment of the current home and potential upgrades is required.
Frequently Asked Questions
No. The NatHERS thermal star rating assesses the modelled thermal performance of the building shell and is expressed as a rating out of 10 stars. The Whole of Home rating assesses major household energy uses, onsite solar generation and battery storage and is expressed as a separate score out of 100. The two ratings provide complementary outcomes within the broader NatHERS assessment framework.
The assessment considers heating and cooling equipment, hot-water systems, lighting, cooking and plug loads, pools and spas where applicable, solar photovoltaic systems and battery storage. It also uses the heating and cooling loads produced by the associated thermal model of the dwelling.
A score of 100 represents a net zero energy-value outcome under the NatHERS Whole of Home calculation method. Ratings above 100 are possible where the assessed contribution of onsite energy generation exceeds the modelled energy value associated with the dwelling.
No. The rating uses standardised occupancy, equipment-use and operating assumptions so that proposed homes can be assessed consistently. Actual household consumption and energy costs may vary according to occupant behaviour, weather conditions, energy tariffs, equipment operation and future changes to the dwelling.
Not necessarily. The requirement depends on the project location, building classification, approval pathway and the residential energy provisions adopted by the relevant state or territory. Jurisdictional variations and transitional arrangements may also affect the assessment required for a particular project.
No. New residential projects in New South Wales generally follow the BASIX assessment pathway. A NatHERS thermal rating may support the thermal-performance component of a BASIX submission, but BASIX and a NatHERS Whole of Home rating are not interchangeable certificates.
Solar PV can strengthen the Whole of Home result by offsetting modelled household energy demand. However, it should not be treated as a replacement for an appropriate thermal design and efficient heating, cooling and hot-water systems. A coordinated combination of lower demand, efficient equipment and onsite generation generally provides a more balanced outcome.
Yes. Preliminary modelling can begin using documented design assumptions or provisional system specifications. The model should then be updated as heating, cooling, hot-water, cooking, solar and battery selections are confirmed so the final rating reflects the documentation intended for approval and construction.
Existing homes follow a separate Home Energy Rating pathway. That assessment reflects the existing building and household systems already in place and may also provide guidance about potential upgrades. It should not be treated as the same service pathway as a new-home Whole of Home compliance assessment.
Material changes to the building design, glazing, insulation, heating and cooling equipment, hot-water system, cooking energy source, pool or spa equipment, solar PV or battery storage may affect the assessment result. Relevant changes should be referred back to the assessor so the model and certificate can be reviewed before construction documentation is finalised.
Related Knowledge
Whole of Home sits within the broader NatHERS and residential energy compliance framework. These related guides explain the neighbouring assessment pathways without replacing the specific Whole of Home rating process.
Thermal Rating Framework
Understand the national residential energy-rating framework, thermal star ratings and how accredited modelling supports new-home assessment.
New South Wales
Review the NSW planning pathway for residential water, energy and thermal-performance requirements.
Prescriptive Compliance
Learn how the elemental Deemed-to-Satisfy provisions address residential building fabric, glazing, sealing and services.
Alternative Verification
Understand how Verification Using a Reference Building may support projects requiring an alternative thermal-performance pathway.
Project Review
Send the available plans, project location and household system information for an initial review. Certified Energy can help confirm whether a Whole of Home rating applies and identify the documentation needed for the assessment.
Early assessment can help coordinate the thermal model with heating and cooling, hot water, cooking, lighting, pools or spas, solar PV and battery storage before the design and specifications are finalised.
Last reviewed: June 2026. This page is maintained by Certified Energy as part of its Residential Performance Knowledge Hub.
