As Australia moves toward more energy-efficient housing, the Nationwise House Energy Rating Scheme (NatHERS) Whole of Home Assessment has become a central part of building compliance under the National Construction Code (NCC) 2022 energy efficiency provisions.
This assessment goes beyond measuring the thermal performance of a home; it evaluates the performance of appliances, renewable energy systems, and household energy use to provide a complete picture of energy efficiency.
In this article, we’ll walk through the Whole of Home (WoH) assessment process in detail, from documentation and modelling to interpretation of results.
We’ll also explore the updated NatHERS certificate, explaining what it includes and how it supports builders, designers, and assessors in meeting the NCC 2022 energy efficiency requirements.
Table of Contents
What is the NatHERS Whole of Home Assessment?
The Whole of Home Assessment evaluates the overall energy performance of a dwelling, considering both the building’s thermal shell and the energy use of fixed appliances such as:
- Heating & cooling
- Hot water
- Lighting
- Renewable energy systems such as solar PV and batteries
Unlike the traditional 7-star NatHERS rating, which measures how well a home’s design maintains comfortable indoor temperatures with minimal heating and cooling, the Whole of Home approach assesses total operational energy demand.
This relies heavily on accurate thermal performance modelling.
The WoH assessment is now mandatory for all new homes under the National Construction Code (NCC) 2022, complementing the thermal performance star rating and helping homeowners save on their energy bills.
According to the Australian Building Codes Board, approximately 90% of new home designs in Australia are assessed using the Nationwide House Energy Rating Scheme (NatHERS), and this figure is expected to grow as the Whole of Home framework becomes the new standard for energy efficiency compliance.
This shift aligns with Australia’s broader transition toward net-zero emissions, making the Whole of Home pathway increasingly important for builders and designers.
Learn more about our Whole of Home Assessment services.
Why the Whole of Home Framework Was Introduced
NCC 2022 represents Australia’s most significant update to residential energy provisions in over a decade. These changes were introduced to ensure homes are designed not only for passive comfort, but also long-term operational efficiency.
Under the previous NCC, two homes with identical thermal performance could have vastly different running costs depending on their appliance choices.
The Whole of Home framework closes that gap by linking building design + appliance efficiency + solar generation into one measurable performance score.
This shift supports Australia’s transition toward net-zero housing and ensures more consistent energy outcomes across states and climate zones.
What’s Included in a Whole of Home Assessment?
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Category
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Assessed?
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Examples
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Heating & Cooling
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Split systems, ducted AC, efficiency ratings
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Hot Water
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Solar, heat pump, gas, instantaneous systems
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Lighting
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LED types, control systems, layouts
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Renewable Energy
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PV capacity, inverter efficiency, battery storage
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Pool/Spa Equipment
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Pump size and efficiency
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Cooking Appliances
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Cooktops and ovens
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Non-fixed Appliances
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TVs, fridges, portable heaters
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Step-by-Step Assessment Process
Step 1: Design Documentation and Data Collection
The assessment begins with gathering all relevant design documentation. Assessors require detailed plans and specifications to accurately model the home’s energy performance.
Key documents and data typically include:
- Architectural drawings and elevations showing layout, window and door sizes, and materials
- Mechanical system details, including heating and cooling appliances, capacities, and efficiencies
- Hot water system specifications – e.g. electric, gas, solar, or heat pump
- Lighting layout and specifications, including type, placement, and control systems
- Renewable energy systems, such as solar PV and battery storage
- Additional equipment, such as pool or spa pumps, where relevant
This information forms the foundation for accurate energy modelling, allowing assessors to simulate how the home will operate under typical conditions.
For complex builds, such as multi-unit developments or custom architectural homes, assessors may also request insulation details, shading structures, window performance data (U-values and SHGC), and on-site generation forecasts to ensure high-accuracy results.
Step 2: Using Accredited Tools
Once the data is collected, assessors use NatHERS-accredited Whole of Home software tools, such as HERO, FirstRate5, or BERS Pro, to simulate the home’s energy performance.
These assessment tools integrate building geometry, climate zone data, and appliance efficiency information to estimate annual energy demand across different systems.
The software also models household energy use patterns, such as heating, cooling, lighting, water heating, and on-site energy generation or storage.
The result is a detailed simulation of how the home interacts with the electricity grid, including energy consumption, production, and potential export from renewable systems. This enables assessors to quantify the home’s total operational efficiency in a consistent, measurable way.
Because each software tool interprets appliance data slightly differently, assessors often compare outputs or run sensitivity checks to ensure the final model accurately reflects real-world performance.
Step 3: Generating the Whole of Home Rating
The Whole of Home performance rating is expressed as a numerical score out of 100, representing the home’s overall energy efficiency.
A score between 60 and 70 typically indicates that the home meets NCC 2022 compliance benchmarks.
Homes scoring above this range demonstrate improved efficiency, often achieved through high-performance appliances, better insulation, and integration of renewable energy systems.
The Whole of Home rating allows project teams to see at a glance how the dwelling performs across key energy categories, helping designers and builders confirm that both thermal performance and appliance efficiency targets are being met.
Homes that significantly outperform the benchmark may be eligible for additional sustainability credentials or rebates, depending on state or federal programs.
Step 4: Review and Optimise
An important benefit of the Whole of Home framework is the ability to iteratively refine the design to achieve a better score.
Assessors and designers can explore scenarios to improve energy efficiency, such as:
- Replacing a conventional water heater with a heat pump system
- Upgrading lighting to LEDs
- Installing solar panels or battery storage to offset energy demand
- Adjusting appliance selections or insulation values to enhance thermal comfort
This iterative process not only supports NCC energy efficiency compliance but also gives project teams a clear pathway to optimise performance requirements and reduce future operating costs.
Builders often use this stage to balance cost and performance, identifying which upgrades offer the greatest improvement for the least additional expense.
Understanding the Updated NatHERS Certificate
The updated NatHERS certificate introduced alongside the Whole of Home framework provides a more detailed and transparent summary of a dwelling’s energy performance.
Key elements include:
- Thermal star rating – representing the building’s passive thermal efficiency
- Whole of Home score – a numerical measure (out of 100) of total operational energy performance
- Appliance breakdown – showing estimated energy use for heating, cooling, hot water, lighting, and on-site generation
- Heating and cooling load limits – ensuring compliance with climate zone benchmarks
This expanded certificate format serves as clear documentation for certifiers, builders, and regulators, supporting both the design approval process and ongoing compliance verification.
The certificate also helps homeowners understand long-term running costs, potential savings, and the benefits of selected appliances or renewable systems.
For project teams, it offers enhanced transparency and communication with clients, showing not only that the home meets regulatory requirements but also how each design decision contributes to sustainability outcomes.
Explore our NatHERS Assessment Services.
Common Questions and Practical Considerations
Can you change appliances after getting your Whole of Home assessment?
Yes, but any changes that affect energy use, such as different heating, cooling, or hot water systems, may require an updated simulation to ensure continued compliance.
What if final selections differ from what was modelled?
If there’s a discrepancy between modelled and installed appliances, a reassessment may be needed before the final Occupancy Permit or Certificate of Compliance is issued.
Is resimulation needed before final certification?
In most cases, yes. The final certificate must reflect actual installed systems to meet NCC documentation requirements.
What’s the role of AAOs (Accredited Assessor Organisations)?
AAOs oversee assessor accreditation, software training, and quality assurance, ensuring consistency across all NatHERS Whole of Home assessments.
Can assessors complete both the thermal rating and Whole of Home assessment?
Yes. Most accredited NatHERS assessors are trained to deliver both components, providing a streamlined, integrated compliance service for builders and designers.
How does the Whole of Home score relate to the 7-Star rating?
Do renovations or extensions need a Whole of Home assessment?
Major renovations or additions that trigger a new building permit typically require compliance with the same NCC 2022 energy efficiency standards, including Whole of Home modelling.
What happens if a home fails to meet the required score?
The assessor can provide recommendations to improve the rating, such as upgrading appliances, improving insulation, or adding renewable energy, before resubmitting for compliance.
Conclusion
Understanding the Whole of Home assessment process is essential for anyone involved in residential building design and compliance.
By modelling both the thermal envelope and operational energy systems, it delivers a complete picture of a home’s performance, supporting NCC 2022 energy efficiency requirements and helping Australia move toward net-zero housing standards.
For builders and designers, understanding the Whole of Home process is key to streamlining building approvals, avoiding compliance delays, and designing homes that perform efficiently in real-world conditions.
Green Choice Consulting works closely with project teams to deliver accurate NatHERS assessments and Whole of Home ratings, tailored to meet NCC 2022 energy efficiency targets across all Australian climate zones.
For expert advice, accurate thermal performance modelling, and practical guidance through every stage of compliance, contact Green Choice Consulting on 1300 864 944.
Albert Burton is the founder of Green Choice Consulting, leading a national team that delivers fast, accurate ESD reports for residential and commercial projects. With expertise in sustainability and business, he leverages advanced technology to streamline compliance and reduce costs for clients.