Free NatHERS Home Energy Rating Calculator

Estimate your result

How to use this calculator

You don't need any technical knowledge to use this tool. Work through the fields below in order — most people can complete it in under two minutes using rough figures from a plan or even a general idea of their design. Tap or hover the i next to any field for a plain-language explanation of what it means and how to choose a value. As you adjust each field, the result panel updates instantly on the right (or above, on mobile), so you can experiment freely to see what actually moves the needle.

Inputs

Site address i Optional. Adding this helps us give more accurate follow-up advice if you request a full assessment, but it doesn't affect the estimate itself.

Climate zone i Choose the option closest to where you're building. If you're not sure which zone you're in, pick the nearest city listed and it'll be close enough for an estimate.

Conditioned floor area m² i The total floor space inside your home that will be heated or cooled — generally everything except garages, alfrescos, and unenclosed areas. Drag the slider to roughly match your home's size in square metres.

180 m²

Window-to-floor ratio i Roughly how much of your home's floor area is made up of window glass. A typical home sits around 15–25%. More glass generally means more heat gain and loss, unless it's offset by better glazing or good shading.

22%

Glazing performance i The type of windows specified. Single glazing is the most basic and least efficient; double glazing is now standard in most new homes; Low-E (low-emissivity) coated glass and triple glazing perform better again. If you're not sure yet, "Double, std" is a safe default for a typical new build.

Ceiling insulation i Insulation performance is measured in "R-values" — how well a material resists heat flow. Higher R-value means better insulation. If your plans or builder's spec sheet mention an R-value, select the closest match; if you don't know yet, the mid-range option is a reasonable starting point for a standard new home.

Wall insulation i Also measured in R-values — higher means better resistance to heat flow. Match the closest R-value from your plans or spec sheet, or use the mid-range option as a reasonable starting point if you're unsure.

Construction / thermal mass i How much your building's materials store and slowly release heat. Lightweight construction (like standard timber frame) heats and cools quickly, while heavier construction (like brick or concrete) evens out temperature swings over the day. Choose "Mixed" if you're unsure — it's the most common combination in Australian homes.

Roof colour i Darker roofs absorb more heat, which matters more in hotter climates. Pick whichever is closest to your actual or planned roof colour.

Orientation of main living i The compass direction your main living space faces. North-facing living areas generally perform best in most WA climate zones, since they're easiest to shade in summer and warm in winter.

Indicative result

7.0 / 10

Comfortably exceeds the NCC 2022 minimum of 7 stars. Suitable for most lender requirements and Green Star residential pathways.

Heating load

34 MJ/m²

Cooling load

21 MJ/m²

vs. NCC minimum

+0.0 stars

Indicative range

±0.5 stars

Engage a NatHERS assessor →

Copy your results and send them to us when you request a quote, so we know your indicative NatHERS results.

Disclaimer

A heuristic only — not a substitute for AccuRate, FirstRate5 or BERS Pro modelling. This estimator is calibrated against recent EcoForm WA NatHERS certificates (mean error ≈ 0.3 stars) and is indicative only. EcoForm provides full NatHERS and Whole-of-Home assessments through accredited BDAV assessors.

From an estimate to a certified rating

The estimator gives you a useful indication, but the number that goes to your certifier and council has to come from accredited NatHERS software, run by a qualified assessor, using your final plans. EcoForm's Residential Energy team prepares certified NatHERS assessments, heating and cooling load modelling, and practical, plain-language advice on insulation, glazing, and passive design for new homes, alterations, and multi-dwelling projects across WA, SA, NT, QLD, NSW, and VIC.

Frequently asked questions

Is this the same as a certified NatHERS assessment?

No. This estimator gives a planning-stage approximation using simplified fabric and orientation inputs. A certified rating has to be produced using accredited software (AccuRate, FirstRate5, or BERS Pro) run by an accredited assessor against your final plans.

How accurate is the estimate?

It's calibrated against recent EcoForm WA NatHERS certificates with a mean error of around 0.3 stars, so it's a genuinely useful early guide — but it isn't a substitute for formal modelling, which accounts for factors like exact window placement and detailed thermal bridging.

What if my design comes back below the required minimum?

It's common, and usually fixable without a full redesign. Small changes to glazing spec, insulation levels, or orientation of living areas often close the gap. Our team can advise on the most cost-effective way to get a design across the line before working drawings are finalised.

Who needs to know their star rating?

Homeowners designing a new build or a significant renovation, extension, or alteration

Owner-builders wanting to understand energy requirements before finalising plans

Builders and draftspeople checking a design early, before committing a client to working drawings

Multi-dwelling developers scoping compliance across a group of similar unit or townhouse designs

What actually moves your star rating?

A handful of decisions have an outsized effect on your final rating:

Insulation in walls, ceiling, and floor

Window and glazing specification — size, orientation, and glass type matter more than most people expect

Orientation of living areas relative to the sun

Airtightness and sealing of the building envelope

Shading, eaves, and thermal mass

Need a formal report?

Move from a quick estimate to a certified assessment.

Call(08) 9555 9444

Writeops@ecoform.com.au

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Free Planning Calculators

Indicative NatHERS star rating

How to use this calculator

From an estimate to a certified rating

Frequently asked questions

Move from a quick estimate to a certified assessment.