Whole-of-House Energy Budget Under NCC 2022 (AU)

What it is

The Whole-of-House energy budget is a new layer of residential energy compliance introduced in NCC 2022 Volume Two Part H6. It sits on top of the 7-star NatHERS envelope rating and assesses the fixed equipment in a new home (heating, cooling, hot water, swimming pool and spa pumps, lighting and on-site PV) against an annual energy use budget per climate zone.

The intent is straightforward. A 7-star envelope alone does not guarantee a low-energy home, because two homes with the same shell can have very different running costs depending on the heating, cooling and hot water choices. The Whole-of-House budget closes that gap by setting a maximum total energy load and crediting any on-site generation.

How the budget works

Climate-zone specific budgets

Part H6 sets an annual energy budget in megajoules per square metre, varying by NCC climate zone. The budget is the ceiling. The proposed home's modelled load (heating + cooling + hot water + lighting + pool pump if any) minus on-site PV generation must come in under the budget.

This is calculated using NatHERS Whole-of-House software, which extends the same accredited tools (AccuRate, FirstRate5, BERS Pro) into the equipment side. The same assessor who produces the envelope rating typically produces the Whole-of-House report.

Equipment classes assessed

The Whole-of-House calculation looks at fixed building services. Heating system type (reverse-cycle, gas, electric resistance) and efficiency matter. Cooling system efficiency matters. Hot water system type and source (heat pump, solar, gas, electric storage) is a major driver. Fixed lighting wattage and pool or spa pump energy are included.

Plug-in appliances like fridges, washing machines and TVs are excluded because the homeowner controls those after handover.

On-site PV is a credit

Rooftop solar PV is included as a negative load against the budget. The modelled annual generation from the as-designed PV array is subtracted from the equipment load. This means a home with marginal heating or hot water choices can still pass Whole-of-House by sizing the PV system appropriately.

How this changes the build

The Whole-of-House budget creates real design pressure on three items: hot water (heat pumps over gas storage), heating and cooling (reverse-cycle over gas or resistance) and PV sizing. Builders working in cold climate zones often need to specify a heat pump hot water system and a reverse-cycle ducted system to pass without an oversized PV array.

Documentation requirements

The Whole-of-House report is now a building permit document in jurisdictions that have adopted NCC 2022. It sits next to the NatHERS Universal Certificate and is referenced at occupation. As-built variations to the equipment specification require a re-rating before practical completion.

How TradeLens checks this

TradeLens flags a Class 1 building permit where the Whole-of-House report is missing, the modelled equipment does not match what is installed, the PV sizing on the rating does not match the as-built system, or the equipment substitutions on site were never re-rated.

Common compliance gaps

The recurring gaps are last-minute swaps from heat pump to gas storage hot water, ducted heating replaced with split systems without re-rating, PV systems downsized in value engineering, and lighting allowances exceeded by additional fittings added during fit-off. Each of these breaks the Whole-of-House calculation and the home is no longer compliant against its own permit.