Whole of Home assessment and rating

As of 1 May 2024, Modern Homes residential energy efficiency standards include a 7-star thermal performance rating for houses and units and a Whole of Home rating to measure the energy use of the home.

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

There are many appliance combinations that can be used to achieve a high Whole of Home rating. An efficient water heating system and appropriately-sized space heating or cooling systems can save money and ensure the home is comfortable and resilient in hot and cold climates. On-site renewable energy generation 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.

The National Construction Code 2022 (NCC) Modern Homes residential energy efficiency standards were implemented in Queensland through amendment of the Queensland Development Code 4.1 – Sustainable buildings.

What is included in a Whole of Home assessment?

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

• Lighting
• 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 rating

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

Whole of Home ratings and requirements

The Whole of Home rating scale ranges from 0 to 100. A poor energy-performing home would rate under 40, while a score of 100 is a net zero energy value home. A rating over 100 is possible where the home is producing more energy than it uses. Ratings at 100 or above indicate the home will have low or no energy bills.

The new energy efficiency standards mean new houses and townhouses will need to achieve a Whole of Home rating of 60 and new units a rating of 50.

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 decentralised, but currently does not offer a Whole of Home option for apartments with centralised services. However, the NatHERS Administrator expects that software tools will be available to assess Class 2 buildings with centralised services from 2025.

All new assessments must be done using the latest version of software unless an exemption is provided by the relevant building authority.

Deemed to Satisfy Elemental Provisions

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

This compliance option is prescribed in Australian Building Codes Board NCC 2022 as follows:

• for houses in the DTS Provisions of Volume Two, H6D2(2)(b)
• for apartments in the 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 water heaters.

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.

Also consider...

• Learn more about the NatHERS Whole of Home rating to understand how it can be used to measure energy use.
• See the Modern Homes provisions for more information and guidance materials
• Read more about what's new to the National Construction Code 2022.