Whole-Of-Home Energy In NCC 2022: The Budget That Prices Your Appliances Before You Build

YOUR ENERGY BUDGET STARTS BEFORE APPLIANCES ARRIVE.Check whole-of-home requirements before choosing the specification.

Energy compliance on a new dwelling used to be one number: the star rating. NCC 2022 kept that number, raised it, and then added a second test that behaves very differently. The whole-of-home energy budget looks at the fixed appliances you specify, not just the thermal shell around them, and it is calculated before the house is built. If your feasibility priced a star rating and stopped there, this is the line item that moves.

The deal question: what did your specification actually assume?

A star rating is a property of the building envelope as modelled. The whole-of-home test asks a separate question: across a year, does the energy used by the heating and cooling, hot water, cooking, lighting and pool or spa pumps stay within an allowance for a dwelling of that size? Part 13.6 of the ABCB Housing Provisions sets that out. Clause 13.6.1 states the Part applies to a Class 1 building and a Class 10a building with a conditioned space, and clause 13.6.2 requires the building's net equivalent energy usage to not exceed an allowance built from a floor area factor, efficiency factors, pool and spa pump energy, and any renewable energy the design includes.

That last term is why the appliance schedule and the roof plan now talk to each other. You can meet the budget by choosing more efficient appliances, by adding renewables, or by a combination, and the cheapest answer for one site is not the cheapest answer for the next.

Why the star rating and the budget are not the same test

It is easy to read "seven stars" and assume the work is done. It is not. Section 13 of the Housing Provisions places the whole-of-home provisions beside, not inside, the fabric, glazing, sealing and services parts, and Volume Two Section H carries the energy-efficiency requirements for Class 1 and 10 buildings with Specification 42 for the house energy rating software path. A design can clear the thermal load limits and still need a better hot water unit or a different cooker to clear the annual budget.

Practically, that means the two results need to be read together at the same time. Ordering a rating early and then swapping the appliances to save money later is how a design ends up non-compliant on paper that has already been through a certifier.

What the whole-of-home budget is designed to capture

The ABCB's own summary of the change explains the intent: the minimum thermal performance level rose to the equivalent of seven stars, and a new whole-of-home annual energy use budget was introduced to be met by new homes. The budget addresses the energy use of heating and cooling equipment, hot water systems, cooking appliances, lighting, and swimming pool and spa pumps. Renewable energy systems such as rooftop solar panels and batteries are not mandatory but can be factored into the calculation.

Read that as a specification checklist. Every one of those items is something a buyer or a tenant notices, and every one of them has a price gap between the cheapest compliant option and the option a designer might prefer.

The site test a capable student would run

1. Confirm the applicable edition and date with the certifier before you brief the designer, using the ABCB adoption table as the starting map rather than as the answer for your site.
2. Model early and model both tests. Ask for the star rating and the whole-of-home result from the same assessment so the appliance list is priced with the shell, not after it.
3. Write the appliance schedule into the tender. Hot water, space conditioning, cooking and pool or spa pumps are the inputs the calculation reads, so a builder substitution after contract can invalidate the certificate.
4. Price the gap. Compare the cheapest compliant appliance set against the set in the design, and put the difference in the feasibility as a cost, not a hope.
5. Check the renewable assumption. If the design counts solar towards the budget, confirm the array is actually specified on the roof plan and not left as an optional extra for the buyer.

The trap: treating an energy budget as a paperwork exercise

The common failure is a certificate produced from a modelled house that does not match the house that gets built. When the hot water unit is swapped to a cheaper model, or the solar drops off the plan, the design that was certified is no longer the design on site. On a small project that is not a technicality: it can surface at occupation certificate stage, when the schedule and the certificate no longer agree.

What you do not have to work out alone

You do not need to run the modelling or interpret the clause yourself. An accredited NatHERS assessor produces the rating and the whole-of-home result, and it is NatHERS that underwrites the certificate a certifier accepts. Your job is the deal-level one: make sure the specification you approved is the specification that gets priced, tendered and built, and that the certificate is produced from that design rather than from an earlier draft.

Do that and the energy budget stops being a late surprise. Skip it and the second test arrives after the contract is signed, when changing an appliance or a glazing system costs more than it would have at design stage.

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Photo: Houses in Corinda, Queensland, 2021, Wikimedia Commons, CC BY-SA 4.0.