Whole of Home assessment and score

From 1 May 2024, Modern Homes residential energy efficiency standards include:

  • a 7-star thermal performance rating for new houses and units
  • a Whole of Home score (out of 100) to assess the energy budget of the dwelling’s major fixtures and appliances, including any solar photovoltaic (PV) energy system.

Whole of Home assessments aim to lower energy costs by helping homeowners make cost-effective choices about their home's major fixtures and appliances.  Homeowners, designers and builders can explore the trade-offs and benefits of different technologies and appliance efficiencies that works for them and their budget.

There are many appliance combinations that can be used to achieve a high Whole of Home score. An efficient water heating system (solar or heat pump) and appropriately-sized space heating or cooling systems can save money and ensure the home is comfortable and resilient in hot and cold climates. Inclusion of a solar PV energy system can also help offset the home's energy use.

The relationship between a home's thermal performance rating and its Whole of Home rating means that increasing thermal performance will increase the Whole of Home rating. This is because the heating and cooling energy needs will be lower in a home with a higher thermal performance rating.

What is included in a Whole of Home assessment

A Whole of Home assessment involves the following fixture and appliances:

  • artificial lighting
  • mechanical heating and cooling
  • hot water
  • swimming pool and spa pumps
  • cooking and plug-in appliances.

Onsite energy generation and storage (e.g. solar PV and battery) can also form part of a Whole of Home assessment where they are included in the design documentation.

Calculating a Whole of Home score

In simple terms, the assessment considers the energy used in a household for heating, cooling, appliances and equipment, minus any energy generated from solar PV. This assessment builds a useful snapshot of household energy costs as well as its carbon emissions.

Whole of Home ratings and requirements

The Whole of Home score ranges from 0 to 100 – a poor energy performing home would rate under 40, while a score of 100 is a net zero energy home. A score over 100 is possible where the home is producing more energy than it uses i.e. where it includes a large solar PV system.

A new house needs to achieve a minimum Whole of Home score of 60 (out of 100) and a new unit apartment needs to achieve at least 50 (out of 100).

Compliance options

The 2 main existing compliance options available to house energy assessors for Whole of Home assessments are:

NatHERS software

The same software tools used for thermal performance assessments are used for assessing compliance with the NCC Whole of Home energy efficiency requirements.

The following software tools have been accredited by NatHERS for use in performing Whole of Home assessments and issuing Whole of Home certificates:

  • BERS Pro
  • AccuRate Home
  • Home Energy Rating Optimisation (HERO)
  • FirstRate5.

NatHERS-accredited software is able to provide a whole of home rating for apartment units where hot water and space conditioning are self-contained in the unit, but currently does not offer a Whole of Home option for apartments with centralised services.

Deemed to Satisfy Elemental Provisions

This option provides a prescriptive approach to complying with the Whole of Home requirement. Following all the elemental provisions of the NCC creates a deemed to satisfy (DTS) solution.

The elemental provisions are provided in NCC 2022 as follows:

  • for houses – DTS Provisions of Volume Two, H6D2(2)(b)
  • for apartments – DTS Provisions of Volume One, J2D2(3)(a)(i), (b) and (c).

Whole of Home energy savings tips

The most important appliances affecting a Whole of Home assessment are heating/cooling and hot water, as on average they account for 40% and 23% of annual power demand, respectively.

Air-sourced heat pumps and air conditioners deliver 3 to 5 times more space heating or cooling energy than they consume in power and provide a major boost to a Whole of Home rating. This energy consumption outcome is similar for heat pump hot water systems.

A 5-watt LED lightbulb produces the same amount of light as a 75-watt incandescent lightbulb, while using 93% less energy, resulting in higher energy efficiency.

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