What is a BASIX certificate and do I need one in NSW?

A BASIX (Building Sustainability Index) certificate is mandatory for all new residential buildings and alterations in NSW with a construction value over $50,000. It verifies compliance with water, thermal performance and energy efficiency targets. A BASIX certificate is required for both Development Applications (DA) and Complying Development Certificates (CDC).

How much does a BASIX certificate cost in Sydney?

BASIX certificate costs in Sydney range from $250–$800 depending on project complexity. Simple single dwellings typically cost $250–$400, while multi-residential or mixed projects requiring thermal modelling can reach $600–$800. This is separate from the BASIX assessment fee charged by the NSW Planning Portal at lodgement.

What are the 7-star NatHERS requirements in NSW?

From 1 October 2023, all new homes in NSW must achieve a minimum 7-star NatHERS rating under the National Construction Code 2022. This measures the thermal performance of the building envelope (walls, roof, floors, windows) and glazing. Higher ratings (7–10 stars) mean less heating and cooling energy is needed, reducing running costs and improving comfort.

How can I improve my BASIX score?

Key strategies to improve BASIX scores include: (1) Installing solar PV and battery storage, (2) Using high-performance insulation and double glazing, (3) Selecting water-efficient fixtures (4-star WELS-rated taps, showers, toilets), (4) Incorporating passive design principles (orientation, cross-ventilation, thermal mass), (5) Using light-coloured roofing to reduce heat absorption, and (6) Implementing rainwater tanks for garden and toilet use.

BASIX & NatHERS assessments for NSW homes and DA/CDC lodgement

Design-integrated BASIX and NatHERS for Sydney and Greater NSW — DA and CDC lodgement support by giantA Pty Ltd.

BASIX is NSW’s sustainability certificate for water, energy and thermal compliance on new residential work and alterations valued at $50,000 or more (and/or a pool or spa of 40,000 litres or more). NatHERS rates thermal performance and often feeds the BASIX Simulation path. giantA prepares both with design support for Sydney and Greater NSW DA and CDC lodgement.

Modern NSW home cutaway showing solar, HVAC and energy flows — BASIX energy

When do you need a BASIX certificate in NSW?

You need a BASIX certificate when your project sits on the NSW residential pathway that triggers the Building Sustainability Index. Under NSW Planning Portal rules, BASIX applies to new residential developments, to alterations and additions valued at $50,000 or more, and/or where you install a pool and/or spa with a total volume of 40,000 litres or more. The certificate is lodged with development applications (DA) and complying development certificates (CDC). Always confirm the current triggers on the NSW Planning Portal BASIX hub and the alterations and additions page.

New dwellings and multi-dwelling / Class 2

New houses, dual occupancies, townhouses and other multi-dwelling residential work commonly need BASIX before lodgement. Class 2 (apartment / multi-res) projects on the residential BASIX pathway also need coordinated certificates — often with unit-level thermal modelling where Simulation is used. That stream is separate from Design and Building Practitioners (DBP) / registered design practitioner documentation. For Class 2 design and RDP coordination, see our Class 2 building design NSW service.

Alterations & additions ($50,000 or more) and pools/spas (40,000 L or more)

Renovations and additions are not exempt from BASIX by default. The Portal states BASIX applies to alterations and additions valued at $50,000 or more and/or pool/spa installations of 40,000 litres or more. If you are budgeting a reno or extension, pair this check with our renovation & extension Sydney and cost estimating services so construction value and the BASIX trigger stay aligned.

Ready to check whether BASIX applies to your drawings? Request a BASIX / NatHERS review.

BASIX vs NatHERS

BASIX is the NSW Government sustainability certificate that sets water, energy and thermal commitments for applicable residential work. NatHERS (Nationwide House Energy Rating Scheme) is the Australia-wide thermal performance rating and modelling framework. In NSW, NatHERS outputs commonly supply the thermal inputs when you use the BASIX Simulation method — so the two systems work together, rather than as rivals.

	BASIX	NatHERS
Who runs it	NSW Planning Portal BASIX tool; prepared with consultant support as needed	NatHERS assessors using NatHERS-accredited software such as AccuRate Home and FirstRate5
What it covers	Water, energy and thermal commitments for NSW residential compliance	Heating and cooling thermal performance and star rating
Certificate type	BASIX certificate (lodged with DA/CDC)	NatHERS certificate / thermal report
When it is needed	When Portal triggers apply (new residential; alterations of $50,000 or more; and/or pool/spa of 40,000 litres or more)	When Simulation (or another assessor-led thermal path) is used to satisfy BASIX thermal — not always required for every DIY thermal path
Geography	NSW-specific	Nationwide scheme; used inside NSW BASIX Simulation

DIY, Simulation, and Passive House (when you need a NatHERS assessor)

BASIX offers more than one thermal pathway. Owner-facing, the three names you will hear are:

DIY method — suitable only where the design fits Portal DIY thermal limits. Complex glazing, orientation or form may take DIY off the table or make targets hard to meet.
Simulation method — thermal performance is modelled in NatHERS-accredited software such as AccuRate Home and FirstRate5, and the results are loaded into BASIX. This is where a NatHERS assessor is typically required. See the Portal Simulation method page.
Passive House standard method — an alternative thermal path recognised by BASIX for qualifying designs; confirm eligibility on the Portal method pages before you commit.

giantA helps you choose the honest method for the drawings you have — not the method that merely looks quickest on paper. Where Simulation is required, modelling uses NatHERS-accredited software such as AccuRate Home and FirstRate5.

For NSW houses (Class 1), use BASIX for planning approval and NatHERS where the Simulation method is used. The national 7-star NatHERS thermal target sits under NCC housing energy rules (Part H6), not commercial Section J. Section J applies mainly to non-residential buildings and apartment SOUs under Volume One.

What giantA delivers

giantA Pty Ltd prepares design-integrated BASIX and NatHERS packages for homeowners, boutique builders and small developers across Greater Sydney and NSW — aimed at getting DA and CDC documentation across the line, not dropping a PDF and walking away.

Typical package:

BASIX certificate preparation in the NSW Planning Portal tool
NatHERS modelling and report where Simulation (or assessor-led thermal) is required — using NatHERS-accredited software such as AccuRate Home and FirstRate5
Design advice to meet water, energy and thermal targets (glazing, insulation, shading, hot water, services intent)
Coordination notes for DA or CDC lodgement sets
Multi-dwelling / Class 2 experience where residential BASIX applies, with a clear handoff to DBP/RDP work via our Class 2 service

What we need from you

Architectural plans, elevations and sections
Window/door and glazing schedules; insulation notes
Hot water, heating/cooling and lighting intent
Site address (climate-zone context)
Whether you are lodging DA or CDC
Construction cost indication for alterations (to check the $50,000 trigger)
Pool/spa volume if relevant

Turnaround & fees

After all design details are complete (plans, schedules and services intent), a single-dwelling BASIX / NatHERS package typically turns around in 24–48 hours; multi-dwelling and Class 2 work takes longer. Incomplete schedules are the usual delay. Fees are quoted as a fixed proposal after drawing review. The NSW Planning Portal certificate fee is separate from giantA’s professional fee.

How this fits your DA or CDC

Confirm BASIX applies (new dwelling; alteration of $50,000 or more; and/or pool/spa of 40,000 litres or more).
Choose thermal method (DIY, Simulation, or Passive House) against Portal rules.
Complete NatHERS modelling where Simulation applies.
Enter commitments in the BASIX tool and generate the certificate.
Lodge the certificate with your DA or CDC package; commitments become approval conditions that the certifier will check on site.

BASIX (and NatHERS Simulation where used) may be required for both DAs and CDCs in NSW when the project is BASIX-affected—check your pathway with council or a certifier. We support compliant lodgement; we do not promise faster determination times.

Why design-integrated assessment helps

A certificate-only pass can still force expensive redraws if targets were never tested against your plan. Design-integrated assessment loops thermal and water/energy commitments through the drawings early — fewer late surprises on Western Sydney heat load, glazing ratios, or hot-water choices. That is the difference between a marketplace assessor listicle and giantA’s approvals packaging.

Official NSW resources

Related guides & services

FAQs

When do I need a BASIX certificate in NSW?

You need a BASIX certificate for new residential developments in NSW, for alterations and additions valued at $50,000 or more, and/or where a pool and/or spa has a total volume of 40,000 litres or more. It is required on both DA and CDC pathways. Confirm current rules on the NSW Planning Portal BASIX hub and the alterations and additions page.

What is the difference between BASIX and NatHERS?

BASIX is the NSW sustainability certificate covering water, energy and thermal compliance commitments. NatHERS is the nationwide thermal performance rating and modelling scheme. In NSW, NatHERS outputs commonly support the BASIX Simulation thermal method. For NSW houses (Class 1), use BASIX for planning approval and NatHERS where the Simulation method is used.

Do I always need both BASIX and NatHERS?

Most NSW residential projects need a BASIX certificate. A separate NatHERS assessment is required when using the Simulation method (e.g. many multi-dwellings and complex designs); some single dwellings can use the BASIX DIY thermal method instead.

How long does a BASIX / NatHERS package take?

After all design details are complete, a single-dwelling package typically turns around in 24–48 hours; multi-dwelling and Class 2 projects take longer. Incomplete schedules are the usual delay.

Can giantA support BASIX for Class 2 / multi-dwelling projects?

Yes. We prepare multi-dwelling BASIX packages with unit-level thermal modelling where Simulation requires it. DBP / registered design practitioner documentation is a separate scheme — we coordinate via our Class 2 building design NSW service when you need both streams.

Request a BASIX / NatHERS review — send your plans for a scoped proposal: Contact giantA.