Table of Contents
- What You'll Need Before You Apply for a BASIX Certificate
- Step 1: Confirm Your Project Needs a BASIX Certificate
- Step 2: Understand the BASIX Assessment Requirements
- Step 3: Choose Who Can Issue Your BASIX Certificate
- Step 4: How to Improve BASIX Water Scores Before You Lodge
- Step 5: What a BASIX Certificate Cost Actually Covers
- Step 6: Lodge, Attach and Avoid Common Mistakes
- Conclusion
- Frequently Asked Questions
Last Updated: September 14, 2026
What You'll Need Before You Apply for a BASIX Certificate
A BASIX certificate is a compliance document that confirms a residential development in New South Wales meets minimum targets for water use, energy consumption and thermal comfort (BASIX | Planning Portal). It must be issued by an accredited assessor and lodged with your development application. At House Energy Certified, we prepare these certificates for architects, developers and builders, helping them achieve first-attempt council approval.
Before you can apply for a BASIX certificate, you need a complete set of architectural drawings, a clear specification of fixtures and materials, and a site address. The certificate is generated from a software assessment, so the inputs must match what you actually intend to build.
Most applications stall because the drawings are incomplete or the specification changes after the certificate is issued. Fix that early and the rest of the process moves quickly.
Here's what you need in hand:
- Scaled floor plans and elevations, marked with the site orientation
- Window and glazing schedule with frame types and sizes
- Hot water system type, capacity and location
- Fixture schedule: taps, showers, toilets and any rainwater or greywater systems
- Roof plan and insulation specification
- Confirmation of whether the project is a new dwelling, alteration, addition or pool
Get these wrong and you'll be re-lodging. Get them right and a certificate can be issued quickly.
Step 1: Confirm Your Project Needs a BASIX Certificate
A BASIX certificate is required for most residential development in New South Wales, but not all of it. The BASIX requirements on the NSW Planning Portal set out exactly which project types are captured.
The rule of thumb: if you're building a dwelling or altering one in a way that changes its water or energy performance, you almost certainly need one. Confirm before you commission anything.
New Dwellings, Alterations and Additions
New dwellings always need a BASIX certificate, including dual occupancy and multi-dwelling housing. Alterations and additions need one when the work affects the dwelling's water or energy use, which most habitable extensions do.
The threshold question is whether the work changes the building's thermal envelope, its fixtures, or its services. Add a bedroom and you've changed all three.
Swimming Pools and Outbuildings
Swimming pools and spas require a BASIX certificate because of their water and energy demand. Detached outbuildings generally do not, unless they contain a habitable room or a service that triggers assessment.
If you're unsure, check the project type against the BASIX project definitions before you spend money on an assessment.
Step 2: Understand the BASIX Assessment Requirements
BASIX assessment requirements come down to three scored areas: water, energy and thermal comfort. Each has a target the design must meet or beat. Miss any one and the certificate cannot be issued.
The software compares your design against a reference building of the same size, type and location. Your score is the percentage improvement over that benchmark.
Energy, Water and Thermal Comfort Targets
Energy targets cover heating, cooling, hot water, lighting and appliances. Water targets cover fixtures, outdoor use and any alternative supply. Thermal comfort is assessed through a NatHERS-style simulation of how the home performs across the year.
The three areas interact. A larger glazed area can lift thermal comfort but push energy demand up. A rainwater tank helps the water score but does nothing for energy.
This is why BASIX often requires careful consideration of design changes. Design changes ripple across all three scores, and an assessor who understands the interaction can help optimise solutions.
Step 3: Choose Who Can Issue Your BASIX Certificate
Only an accredited BASIX assessor can issue a certificate. Accreditation is granted by the NSW government, and the assessor's name and accreditation number appear on the certificate itself.
That means you're not choosing a software tool, you're choosing a person and a process. The difference between assessors shows up in turnaround time, how well they read your drawings, and whether they flag cost issues before you lodge.
Assessors vary in how they handle design changes. Some issue the certificate and disappear. Others stay engaged through council queries, which can help prevent project delays.
House Energy Certified works with architects, developers and builders across the state, and our assessors review the drawings against the specification before anything is lodged. This check helps prevent re-lodgements.
Step 4: How to Improve BASIX Water Scores Before You Lodge
The fastest way to improve BASIX water scores is to reduce demand at the fixture and then offset what remains with an alternative supply. Fixture efficiency is the cheapest lever, and it's usually already in your specification.
Work through it in this order:
- Specify WELS-rated taps, showers and toilets at the highest rating your client will accept
- Add a rainwater tank sized to the roof catchment and the dwelling's demand
- Consider greywater reuse only where the plumbing layout makes it economical
- Reduce irrigated landscape area, or specify drought-tolerant planting
Each of these moves the water score, but the returns diminish. Optimising solutions across all areas is key.
Step 5: What a BASIX Certificate Cost Actually Covers
BASIX certificate cost reflects the assessment work, not a government fee. The assessor's fee covers modelling your design, issuing the certificate and, with a responsive provider, supporting you through council queries.
Pricing depends on project type, dwelling count, design complexity and how many revisions are needed. A single dwelling is a very different job from a multi-dwelling development with shared services.
Be wary of quotes that look unusually low, as they may exclude revisions.
House Energy Certified quotes per project after reviewing the drawings, so the figure you receive reflects the actual scope. Request a free quote and you'll get a clear number rather than a range.
Step 6: Lodge, Attach and Avoid Common Mistakes
Lodging is the straightforward part: the certificate is attached to your development application through the NSW Planning Portal, and it stays valid for the life of the consent. The mistakes happen before that.
The three we see most often:
- Drawings that don't match the certificate. If the lodged plans differ from the assessed design, council will query it.
- Specification changes after issue. Swapping a hot water system or glazing type invalidates the assessment.
- Missing the thermal comfort detail. Insulation and glazing values must be specified, not assumed.
A certificate that aligns with the final plans is a significant predictor of a clean approval. That alignment is a process question.
Conclusion
Energy compliance can cause delays if the certificate and final plans diverge. House Energy Certified exists to address this. We provide BASIX, NatHERS and ESD consulting with fast turnaround, practical thermal performance modelling and cost-saving strategies that keep your budget intact. Our team has delivered over 1000 projects in the last 12 months, and we're trusted by more than 300 architects and developers. Get started with House Energy Certified and keep your project council-ready and on schedule.
Frequently Asked Questions
What information is required to apply for a BASIX certificate?
You'll need architectural floor plans, elevations and site details, plus specifications for fittings such as taps, showerheads, toilets, appliances and any rainwater tank or solar system. Your assessor also needs the dwelling type, floor area, glazing schedule and proposed construction materials. Having finalised plans before the assessment begins is the single biggest factor in avoiding a certificate that doesn't match what you actually build.
How much does a BASIX certificate cost?
BASIX certificate cost depends on the size, type and complexity of your project, plus how many design iterations are needed. A single dwelling with straightforward specifications usually costs less than a multi-unit development or a project that needs several rounds of thermal modelling. Because pricing varies, ask your provider for a fixed quote based on your plans rather than relying on a generic figure.
How long does it take to get a BASIX certificate?
Turnaround depends on how complete your documentation is and how quickly design changes are resolved. A well-documented single dwelling can be assessed within a few business days, while larger or more complex projects take longer, especially if the first assessment falls short and the design needs adjusting. Submitting accurate plans and specifications upfront is the main way to keep the timeline short.
What happens if my project fails the BASIX assessment?
A BASIX assessment doesn't fail in the way an exam does. If your design doesn't meet the energy, water or thermal comfort targets, the assessor identifies which commitments fall short and suggests adjustments, such as improved glazing, a larger rainwater tank or more efficient fixtures. You then revise the design and resubmit. Working with an assessor who models practical, cost-effective changes early can help streamline the process.