What the NCC 'Whole-of-Home' Energy Standard Means for Your New Build
A home that just scrapes through at 7 stars NatHERS can still fail the Whole-of-Home pathway if an electric storage hot water system is selected. Getting both right requires understanding how they interact, and making that call early.
The National Construction Code (NCC) 2022 introduced the 'Whole-of-Home' energy pathway alongside the existing NatHERS thermal rating. Together, they represent a more comprehensive approach to home energy performance, and understanding how they interact is now essential for new home design.
The two-part compliance picture
NatHERS (Nationwide House Energy Rating Scheme) assesses the thermal performance of the building fabric, insulation, glazing, shading, orientation. It gives a star rating of 0–10. WA now requires a minimum of 7 stars.
The Whole-of-Home pathway adds a second assessment layer that considers the energy efficiency of fixed appliances and services within the home. For the first time, the following effect compliance:
• Hot water systems - electric resistive storage systems score very poorly. Heat pump hot water systems or solar hot water with boost score significantly better.
• Heating and cooling systems - the efficiency rating (star rating) of your split system or ducted air conditioning affects your score.
• Lighting - LED lighting throughout is expected. Non-LED systems reduce your score.
• Fixed cooking appliances - in some compliance pathways, the fuel type and efficiency of fixed cooking equipment is assessed.
A concrete example of the interaction
Consider a four-bedroom home in Bunbury that achieves exactly 7.0 stars NatHERS, the minimum. If the builder specifies a standard 250L electric storage hot water system (common and low-cost), the Whole-of-Home assessment may fail, requiring either a different HWS or compensating upgrades elsewhere.
By switching to a heat pump hot water system, at a premium of approximately $1,500–$2,500 over a standard electric unit , the same home comfortably passes the Whole-of-Home assessment. The upfront cost difference is typically recovered in energy savings within 3–5 years.
The flexibility this creates
The two-pathway system creates genuine flexibility for designers and homeowners. A home with excellent fabric performance (8+ stars NatHERS) can tolerate a less efficient appliance selection. Conversely, a home with highly efficient appliances can compensate for fabric performance that's adequate but not outstanding.
The key is understanding the interaction early, before the building contract is signed and the specification is locked in. Decisions about hot water systems, air conditioning brands, and even light fittings now have compliance implications, not just lifestyle and running cost implications.
Frequently Asked Questions
Is the Whole-of-Home assessment mandatory in WA?
Yes. Under NCC 2022, new residential buildings in WA must demonstrate compliance with both the NatHERS thermal rating (7 stars minimum) and the Whole-of-Home energy budget. Both are assessed by an accredited energy assessor.
What is the best hot water system for Whole-of-Home compliance?
Heat pump hot water systems consistently deliver the best Whole-of-Home outcomes in WA's climate. They use approximately one-third of the energy of a standard electric storage system. Solar hot water with a gas boost is also effective. Standard electric storage systems should generally be avoided in new builds.
Does the Whole-of-Home pathway apply to extensions?
NCC 2022 Whole-of-Home requirements apply to new Class 1 dwellings (new homes). Extensions and alterations are subject to different provisions. Consult your building designer or energy assessor for guidance on your specific project.
Ask us how to build smarter, not just to minimum standard, let's design a home that performs well and costs less to run. Contact us at fastlane.drafting@gmail.com
