Residential energy assessment now considers more than the thermal performance of the building envelope. Heating and cooling systems, hot water, lighting, cooking, pool equipment and onsite renewable energy can all influence the wider performance of a new home.
NatHERS Whole of Home was developed nationally to represent this broader energy picture. In New South Wales, however, residential approval continues to operate through BASIX, which has its own Energy score, project commitments and Certificate.
The two systems are related, but they are not interchangeable. Understanding the boundary between the NatHERS thermal star rating, the Whole of Home rating and the BASIX Energy result helps prevent incorrect assumptions during design, documentation and certification.
In Brief
How Do BASIX and Whole of Home Relate?
NatHERS Whole of Home assesses the energy performance of the complete home, including its thermal loads, fixed systems, major appliances, solar generation and battery storage. BASIX uses related whole-home calculation principles within its NSW Energy assessment, but retains a separate score based on the reduction in greenhouse gas emissions compared with a pre-BASIX benchmark. A Whole of Home rating does not replace the BASIX Certificate required for an applicable NSW residential development.
Knowledge Navigation
Understanding the Three Energy Results
Assessment Boundaries
Three Different Results
Thermal stars, Whole of Home ratings and BASIX Energy scores.
NSW Compliance
The BASIX Energy Section
How equipment, fuel, solar and thermal demand affect the NSW score.
National Rating
Whole of Home
What the 0–100+ NatHERS rating represents.
Project Workflow
Coordinate the Whole System
When to resolve the fabric, equipment and renewable-energy strategy.
What Changed in the NSW Residential Energy Framework?
The higher BASIX standards took effect on 1 October 2023. They increased the thermal-performance requirements for many new residential developments and strengthened the Energy standards.
As part of the update, the BASIX Energy methodology incorporated elements of the NatHERS Whole of Home calculation. This helped align the NSW methodology with the broader direction of the National Construction Code while retaining the existing BASIX regulatory framework.
This did not convert BASIX into a NatHERS Whole of Home score. The BASIX Energy result continues to be expressed as a percentage reduction in greenhouse gas emissions compared with the applicable pre-BASIX benchmark.
The updated methodology also changed or refined assumptions relating to occupancy, floor area, lighting and household energy use. The applicable Energy standard continues to depend on factors such as the development type, climate zone and building configuration.
The practical outcome is a more complete assessment of the home’s operational energy systems, while BASIX remains the primary sustainability approval pathway for residential development in NSW.
Assessment Boundaries
Thermal Stars, Whole of Home and BASIX Energy Are Different Results
The three results answer different questions and use different metrics. A project may display more than one of them within its assessment documentation.
| Assessment Result | Primary Question | Metric | Main Inputs |
|---|---|---|---|
| NatHERS thermal performance | How much heating and cooling would the dwelling need to remain comfortable? | Star rating from 0 to 10, supported by heating and cooling loads. | Design, climate, orientation, windows, shading, insulation and construction. |
| NatHERS Whole of Home | How does the complete home perform after its systems, appliances and onsite energy are considered? | Rating from 0 to 100+, using the national energy-value methodology. | Thermal loads, fixed systems, appliances, solar generation and battery storage. |
| BASIX Energy | How much will the development reduce operational greenhouse gas emissions compared with the BASIX benchmark? | Percentage reduction in greenhouse gas emissions. | Thermal demand, systems, fuel types, lighting assumptions, ventilation, pools, solar and relevant shared services. |
What Does the NatHERS Thermal Star Rating Measure?
The NatHERS thermal star rating assesses the building envelope. It estimates the heating and cooling energy required to maintain standardised comfortable conditions across the year.
The thermal model considers factors such as:
- local climate data
- building orientation and geometry
- room layout and zoning
- walls, floors, ceilings and roofs
- insulation and framing
- windows and glazed doors
- solar access and external shading
- thermal mass
- air movement associated with recognised ceiling fans
The star rating does not determine whether the home will use a heat-pump hot water system, gas cooking, solar photovoltaic panels or a particular air conditioner. Those systems sit outside the thermal star-rating boundary.
A higher thermal star rating generally indicates that the dwelling requires less artificial heating and cooling. It does not, by itself, describe the complete energy performance of the occupied home.
National Home Energy Rating
What Does NatHERS Whole of Home Assess?
Whole of Home builds on the thermal assessment by adding the systems and equipment expected to use or produce energy once the home is occupied.
A Whole of Home assessment can consider:
- the heating and cooling demand from the thermal model
- the type and efficiency of heating systems
- the type and efficiency of cooling systems
- hot water systems
- lighting
- cooking equipment
- plug-in appliance assumptions
- pool and spa equipment where applicable
- onsite solar generation
- battery storage
The result is expressed as a score from 0 to 100 or higher. A higher score represents stronger overall energy performance under the national energy-value methodology.
A score of 100 is associated with a net-zero energy-value outcome under the rating methodology. Ratings above 100 are possible where onsite generation produces a sufficiently strong result.
What Does the BASIX Energy Section Assess?
The BASIX Energy section estimates the operational greenhouse gas emissions associated with the proposed residential development.
The score is expressed as a percentage reduction against a pre-BASIX benchmark of 3,292 kilograms of carbon dioxide equivalent per person per year. The project must meet or exceed the applicable Energy standard for its climate and development type.
Energy Input 01
Heating and Cooling
The thermal loads are combined with the selected equipment type, fuel and efficiency.
Energy Input 02
Hot Water
The assessment considers the system type, fuel source and recognised performance.
Energy Input 03
Lighting and Ventilation
Lighting assumptions, exhaust systems, controls and common-area systems can affect the result.
Energy Input 04
Cooking and Other Uses
Cooking systems, clothes drying and eligible appliance inputs form part of the wider energy calculation.
Energy Input 05
Pools and Spas
Pumping, heating, covers and other nominated systems can influence the Energy commitments.
Energy Input 06
Alternative Energy
Onsite photovoltaic systems and other recognised generation can offset relevant electricity emissions.
Methodology
Does BASIX Use the NatHERS Whole of Home Calculation?
The higher BASIX Energy methodology incorporates elements of the NatHERS Whole of Home calculation to help align NSW with the national residential energy framework.
This includes aspects of how occupancy and whole-home energy demand are estimated. The underlying relationship does not mean that the two outputs are identical.
| Question | BASIX Energy | NatHERS Whole of Home |
|---|---|---|
| Regulatory role | Forms part of the mandatory NSW BASIX assessment and Certificate. | Provides a national Whole of Home rating and can support applicable NCC or project requirements. |
| Final result | Percentage reduction in greenhouse gas emissions. | Rating from 0 to 100 or higher. |
| Certificate | BASIX Certificate issued through the NSW Planning Portal. | NatHERS Certificate displaying a Whole of Home result where the additional assessment was completed. |
| Can one replace the other? | No. The BASIX Certificate remains required for applicable NSW development. | No. A Whole of Home rating does not replace the NSW BASIX submission. |
How Thermal Performance Influences Whole-Home Energy
The heating and cooling loads produced by the building envelope form the starting point for the operational energy calculation.
A well-performing envelope generally requires less delivered energy from the heating and cooling systems. A weaker envelope creates greater demand that must be met by the selected equipment.
Building Demand
Thermal Performance
Determines how much heating and cooling energy the dwelling is expected to require under standard operating assumptions.
System Response
Equipment Efficiency
Determines how efficiently the heating and cooling demand is supplied and what energy source is used.
A seven-star result therefore does not guarantee that the BASIX Energy target or a Whole of Home target will be achieved. Inefficient hot water, heating, cooling or pool equipment can still place pressure on the wider result.
Conversely, efficient systems and solar generation do not remove the requirement to satisfy the applicable thermal-performance standards.
Operational Systems
Which Design Decisions Have the Greatest Energy Effect?
Hot water system
Hot water can form a substantial part of residential operational emissions. The system type, fuel, efficiency and any solar contribution can materially influence the result.
Heating and cooling equipment
The thermal loads are combined with equipment efficiency, fuel type and the areas served by the systems.
Cooking fuel
Induction, conventional electric, gas and other recognised cooking arrangements can produce different calculated outcomes.
Lighting and ventilation
Efficient lighting assumptions, exhaust systems and controls influence operational energy, particularly in larger or shared developments.
Pools and spas
Pump efficiency, heating systems, covers and operating assumptions can add significant energy demand.
Solar photovoltaic generation
The system size, orientation and slope influence the amount of modelled onsite electricity generation available to offset relevant household electricity use.
How Does Solar Affect BASIX and Whole of Home?
Onsite solar photovoltaic generation can improve both BASIX Energy and NatHERS Whole of Home outcomes, but the calculations and final metrics are different.
Within BASIX, solar electricity can offset greenhouse gas emissions associated with relevant grid electricity use. The result depends on the nominated array capacity, orientation and roof slope.
Within Whole of Home, onsite generation is considered together with the home’s modelled energy demand. Battery storage can also be represented within the broader NatHERS rating where it forms part of the proposed system.
A larger solar array does not correct every design issue. The home must still satisfy the applicable thermal requirements, and the fixed systems entered into the assessment must remain consistent with the final documentation.
Roof area, orientation, shading, switchboard design, embedded networks and allocation between private and common systems should be resolved before solar is relied upon as a compliance measure.
Fuel and Systems Strategy
Does an All-Electric Home Automatically Pass BASIX?
No. Electrification can support a strong operational-energy strategy, particularly when efficient heat-pump systems and onsite solar are used, but the complete BASIX calculation still needs to be completed.
The outcome depends on the efficiency and configuration of the selected equipment, the thermal loads, the development type, the applicable Energy target and the amount of renewable generation.
A poorly performing electric resistance hot water system can create a very different result from an efficient heat-pump system. Similarly, an inefficient air-conditioning system can place greater pressure on the assessment than a well-selected high-efficiency system.
Gas is not automatically a passing or failing selection either. BASIX assesses the relevant emissions associated with the complete proposed arrangement.
The design team should therefore compare complete system pathways rather than relying only on the broad fuel label.
Does a Whole of Home Rating Replace a BASIX Certificate?
No. BASIX remains part of the NSW planning and approval process for applicable residential development.
A NatHERS Certificate can support the BASIX Simulation Method by documenting the thermal assessment. Where a Whole of Home assessment is also completed, the certificate may display both the thermal star rating and the additional Whole of Home rating.
The BASIX application must still be completed through the NSW Planning Portal. The resulting BASIX Certificate records the water, energy, thermal and applicable materials commitments for the development.
A separate Whole of Home assessment may be useful or required where it forms part of a project brief, national compliance pathway, finance requirement, sustainability objective or voluntary performance target.
Project Documentation
Which Certificate Records Which Information?
| Document | Main Purpose | Typical Information |
|---|---|---|
| BASIX Certificate | Demonstrates that the NSW residential development meets the applicable BASIX standards. | Water, Energy, thermal-performance and applicable materials commitments. |
| NatHERS Certificate | Records the residential thermal assessment completed using accredited software. | Star rating, heating and cooling loads, construction, glazing and thermal specifications. |
| Whole of Home information | Records the broader NatHERS operational-energy assessment where it has been undertaken. | Whole of Home rating, systems, appliances, onsite generation and energy-performance information. |
The documents should describe the same proposed dwelling. Conflicting heating, cooling, hot water, solar or pool-system information can create uncertainty during approval, procurement and occupation certification.
A Coordinated Residential Energy Design Process
1. Establish the thermal design
Review orientation, glazing, shading, construction and insulation while the building form remains flexible.
2. Calculate the heating and cooling demand
Complete the applicable BASIX thermal method and, where required, the NatHERS simulation.
3. Select the fixed systems
Coordinate heating, cooling, hot water, ventilation, cooking and pool systems with the intended design and procurement approach.
4. Review the Energy result
Identify whether the BASIX target can be achieved through the selected equipment or whether further system improvements are required.
5. Coordinate onsite generation
Confirm available roof area, solar orientation, shading and the allocation of any private or common photovoltaic systems.
6. Complete any additional Whole of Home assessment
Where a separate Whole of Home score is required, model the proposed systems, appliances, solar and battery arrangement in the accredited NatHERS software.
7. Transfer the final commitments into the documents
Ensure the plans, schedules, specifications, NatHERS information and BASIX Certificate consistently describe the final design.
Larger Residential Developments
How Does the Relationship Work for Apartments and Townhouses?
Multi-dwelling developments require both dwelling-level and development-level information to be coordinated.
The assessment may need to address:
- individual dwelling thermal ratings
- average and minimum thermal-performance requirements
- individual heating and cooling systems
- central hot water, heating or cooling
- common-area lighting and ventilation
- lifts and other shared services
- communal pools and facilities
- private and common photovoltaic systems
- the allocation of energy systems between buildings or stages
A NatHERS summary certificate can record the thermal result across a building. Where Whole of Home assessments are completed, the summary documentation may also report the relevant Whole of Home outcome.
The BASIX Energy assessment also includes relevant central and common services. These systems must be coordinated with the hydraulic, mechanical, electrical and architectural documentation rather than treated only as dwelling-level appliance selections.
What If the Energy Systems Change After Assessment?
System substitutions can change the BASIX Energy result, the Whole of Home rating or both.
Changes that should be reviewed include:
- changing the hot water technology or fuel
- changing the heating or cooling system type
- selecting equipment with lower efficiency
- changing from induction or electric cooking to gas, or vice versa
- reducing the photovoltaic-system capacity
- changing the solar orientation or available roof area
- removing a battery included in a Whole of Home assessment
- adding or changing pool and spa equipment
- changing central systems or common-area services
- changing the thermal design or heating and cooling loads
A substitution that appears more efficient should still be checked against the actual assessment inputs. Equipment categories, recognised efficiency metrics and fuel assumptions may not be directly interchangeable.
Where the project no longer matches the issued documentation, a revised BASIX Certificate, NatHERS Certificate or Whole of Home assessment may be required.
Why the BASIX Certificate must match the project documents →
Common Misunderstandings About BASIX and Whole of Home
The NatHERS star rating assesses the whole home
The star rating assesses the thermal envelope and heating and cooling demand. It does not include the complete appliance and energy-system profile.
A Whole of Home rating replaces BASIX
BASIX remains the NSW regulatory submission and Certificate pathway for applicable residential development.
BASIX Energy is a score out of 100
BASIX Energy is expressed as a percentage reduction in greenhouse gas emissions. The NatHERS Whole of Home rating uses the 0–100+ scale.
A seven-star home automatically passes the Energy section
The selected heating, cooling, hot water, cooking, pool and renewable-energy systems must also produce a satisfactory Energy result.
Solar can compensate for any design
Solar can improve operational-energy results but does not remove the thermal-performance requirements or every equipment commitment.
All-electric automatically means net zero
The outcome still depends on the thermal demand, equipment efficiencies, household energy assumptions and onsite generation.
Equipment can be selected after the BASIX Certificate is issued
The assessment already relies on nominated system types and performance. Later changes should be reviewed before procurement or installation.
The ratings predict the exact future energy bill
The calculations use standardised assumptions. Actual bills depend on occupancy, tariffs, weather, maintenance and how the household operates the home.
Frequently Asked Questions
BASIX and Whole of Home FAQs
What is NatHERS Whole of Home?
NatHERS Whole of Home assesses the broader energy performance of a new home by combining its thermal loads with heating, cooling, hot water, lighting, appliances, solar generation and battery storage.
Is Whole of Home the same as BASIX?
No. Whole of Home is a national NatHERS rating. BASIX is the NSW residential sustainability assessment and approval framework covering water, energy, thermal performance and applicable material reporting.
Does a Whole of Home rating replace a BASIX Certificate in NSW?
No. An applicable NSW residential development still requires a BASIX Certificate. A Whole of Home rating may provide additional energy-performance information but does not replace BASIX.
How is the BASIX Energy score expressed?
The BASIX Energy score is expressed as a percentage reduction in operational greenhouse gas emissions compared with the pre-BASIX residential benchmark.
What is the difference between a NatHERS star rating and a Whole of Home rating?
The NatHERS star rating assesses the thermal performance of the building envelope. Whole of Home adds the energy systems, appliances, onsite generation and storage and produces a separate rating from 0 to 100 or higher.
Does BASIX use Whole of Home calculations?
The higher BASIX Energy methodology incorporates elements of the NatHERS Whole of Home calculation, including aspects of occupancy and whole-home energy demand. BASIX still produces its own NSW Energy score and Certificate.
Does solar improve both BASIX and Whole of Home?
It can. Solar photovoltaic generation can offset relevant electricity use in both assessments, although the calculation methods and final rating metrics are different.
Can a seven-star home still need Energy upgrades?
Yes. The NatHERS star rating assesses thermal demand. The project may still need more efficient hot water, heating, cooling or pool systems, or onsite solar, to achieve the required BASIX Energy result.
Does an all-electric home automatically pass BASIX?
No. The result depends on the thermal demand, system types, equipment efficiencies, project target and onsite generation. Efficient electrification can support compliance but must still be assessed.
When should the home’s energy systems be selected?
The main heating, cooling, hot water, cooking and solar strategy should be reviewed during design development so the BASIX and any Whole of Home requirements can be coordinated before the plans and specifications are finalised.
Related Knowledge
Continue Exploring Residential Energy Performance
Assessment note: BASIX Energy standards, NatHERS thermal requirements and Whole of Home assessment obligations depend on the project location, dwelling type, approval pathway and current regulatory requirements. A separate Whole of Home rating should not be assumed to replace the BASIX Certificate required for an applicable NSW development.
For current regulatory information, refer to the NSW Planning Portal guidance on the higher BASIX standards and the Home Energy Rating guidance for new-home certificates.
Last reviewed: July 2026.
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