Does One More NABERS Star Mean an Office Building Really Uses Less Energy?

Geoffrey Chen

When Numbers Start Making Decisions · Season Two, “When the Measure Becomes the Target” · Article 10

1. The star comes after the meter, not before construction

A new office can contain efficient air-conditioning, double glazing and sophisticated controls, while its design model predicts excellent performance. After occupation, incomplete commissioning, tenant hours, maintenance and actual operation can leave energy consumption far above the prediction.

The most important design choice in NABERS Energy is to rate twelve continuous months of operational data rather than design intent alone. A NABERS Accredited Assessor applies the rules and compares the building with comparable buildings under relevant climate and use conditions. Offices can receive separate ratings for the base building, a tenancy or the whole building, preventing central air-conditioning, lifts and common lighting controlled by the owner from being confused with tenant equipment. NABERS: “Office Buildings”

Compared with many proxies in this season, the NABERS star sits close to a real outcome. Moving an office from four to five stars normally requires verified evidence of better operational energy performance, not merely completion of a list of efficiency projects.

An improved star does not mean that total energy falls in every circumstance. Hours, floor area, equipment density and climate enter normalisation. The scope may cover only the base building. Grid emissions and renewable supply are a separate dimension. To understand the star, we still need to ask which part of reality it measures.

2. What does NABERS compare?

NABERS uses one to six stars to express operational efficiency relative to a peer benchmark, and a certified rating is valid for twelve months. Official descriptions call three stars average market performance, five excellent and six market-leading. The assessment accounts for floor area, hours of use, climate and other factors relevant to the particular building type. The current office rules are Energy and Water for Offices, version 5.2, April 2025. NABERS: “Energy and Water for Offices Rules”

Normalisation serves fairness. Cooling demand in Darwin differs from Melbourne, and a facility operating around the clock cannot share a raw consumption benchmark with an ordinary office. Without adjustment, organisations would achieve high ratings by selecting favourable uses and locations instead of becoming more efficient.

Normalisation also means a star is not total electricity use. An expanded office can improve efficiency and earn a higher rating while total energy grows. A largely vacant building can consume less without its systems becoming efficient. Professionals need rules that adjust for operational change, while public reporting should still show energy intensity and absolute consumption.

Scope is particularly important. Base building covers central services; tenancy covers the leased space; whole building combines them. If an owner promotes a five-star base-building result and a reader assumes that tenant computers, kitchens and equipment are also five-star, the claim has exceeded the rating. The star should never appear without its scope.

3. How does the number acquire market power?

NABERS is voluntary in many contexts, but Australia’s Commercial Building Disclosure program generally requires a valid NABERS Energy disclosure when office space with a net lettable area of at least 1,000 square metres is offered for sale or lease. Australian Government: “Buildings—owners and tenants”

Disclosure connects an environmental number to leasing and transactions. Prospective tenants can compare efficiency and operating cost. Owners know that poorer performance will become visible at the moment of market choice. The star then affects retrofits, facilities-management contracts, engineering budgets and tenant selection.

The system does not usually command an owner to achieve five stars. It first constructs credible comparison and requires disclosure in an important market. Tenants and investors then incorporate the result into contracts and capital allocation. Procurement policies and green finance can add their own minimums.

This is a relatively gentle path from description to decision. It leaves multiple routes to improvement: commissioning, maintenance, controls, equipment renewal and management of use. Unlike a simple activity target, it places the consequence on the measured outcome.

4. Does the evidence show real change?

Government-commissioned research found that the average NABERS Energy result on certificates issued early in the Commercial Building Disclosure program rose from 3.4 stars in 2011–12 to 4.1 by 2018. NABERS’ 2024–25 annual report says energy intensity in buildings covered by the disclosure program improved 29 per cent over twelve years. NABERS Annual Report FY25

The results support the conclusion that ratings and disclosure occurred alongside genuine efficiency improvement. They do not prove that NABERS alone caused every change. Building codes, technology, energy prices, corporate climate commitments and renewal of the stock also matter. Outside mandatory disclosure, more efficient buildings may be more willing to seek a rating.

NABERS is nevertheless more readily connected with reality than a count of projects. Installing a new chiller is an activity. Lower measured use over the following twelve months is an outcome that enters the next rating. If the retrofit fails in operation, the star does not rise simply because the invoice was paid. Forecasts must answer to operational data.

Annual expiry also prevents one certification from becoming permanent. Equipment ageing, drifting controls and changed use appear in the next assessment. Authority comes from continuing rereading of reality, not from an undated plaque.

5. Where can star-directed optimisation still appear?

First, boundaries can be managed. An owner may emphasise a base-building result and minimise tenant consumption, or search for favourable interpretations of meter separation, rating scope and missing information. Accredited assessment and independent quality assurance are therefore essential.

Second, relative efficiency can be confused with absolute emissions. A star shows energy performance relative to peers; it is not a declaration of zero carbon. From July 2025, NABERS separately displayed a Renewable Energy Indicator showing the proportion of energy supplied from onsite and purchased renewable sources, and stopped allowing GreenPower purchases to change the Energy star. NABERS: “Renewable Energy Indicator”

The separation is sound. Efficiency asks how much energy was required to perform the comparable function. Renewable supply asks where that energy came from. Compressing both into one star would allow renewable purchasing to conceal inefficient operation or high efficiency to conceal fossil dependence.

Third, service quality can be sacrificed. Excessive reductions in heating, cooling, ventilation or lighting can save energy while harming health and work. NABERS has a separate Indoor Environment rating precisely because energy performance needs a non-negotiable service constraint.

Fourth, peer benchmarks evolve. As the market improves, what represents average three-star performance must be updated. Recalibration supports continuing ambition but means stars from different rule and benchmark versions cannot be compared without qualification.

6. Why is NABERS a relatively successful target structure?

It contains several characteristics sought throughout this season. Its measure is close to the final outcome. It uses real operational evidence. Comparison is among peers. Accredited specialists verify data. Ratings expire annually. Scope can be separated. Energy performance, renewable sourcing and indoor environment are not forced into one compensating total. Disclosure gives the number a real consequence in major office transactions.

Most importantly, the main route to a higher score broadly aligns with the public purpose. To gain a star, an owner generally has to reduce standardised operational energy use. Boundaries and benchmarks still require oversight, but a long-term result obtained purely by rewriting an activity record is difficult.

That model cannot simply be copied into education, medicine or justice. Electricity is continuously observed by a meter. Teaching and care have no equally direct sensor. The authority an indicator can safely bear depends partly on how observable the underlying reality is.

Conclusion: one more star usually matters, when read with its scope

For an office reassessed under the same scope and comparable operating conditions, an additional NABERS Energy star will normally represent verified improvement in operational energy efficiency. It is among this season’s clearest cases in which a better number is likely to be a better real outcome.

My judgement is to retain and extend NABERS and Commercial Building Disclosure, while requiring the star to appear with scope, expiry, energy intensity, absolute use and the Renewable Energy Indicator. Indoor environment must operate as a condition that cannot be traded for efficiency. Expansion to tenancies, hotels and other spaces should follow only where peer benchmarks and verification are strong enough.

A good measure does influence behaviour; its influence is aligned with the public purpose. By putting the target after the meter, NABERS prevents a building from earning performance through a promise alone. One way to prevent metric overreach is not to measure less, but to measure as close to the real outcome as possible and require the result to face reality again each year.

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