NABERS UK: EVERYTHING YOU NEED TO KNOW

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Key Insights:

• NABERS provides a verified measure of real-world building performance, using 12 months of operational data rather than predicted outcomes, giving owners a dependable benchmark for efficiency.
• NABERS UK supports both operational and new-build projects, with Energy Ratings for existing offices and Design for Performance (DfP) ensuring new developments meet their intended performance standards.
• Data centres gain particular value from NABERS, as it offers a consistent and independent way to assess cooling performance, PUE, power density, and overall operational efficiency.
• Understanding how to improve NABERS scores starts with high-quality metering and operational optimisation, with cooling efficiency, sub-metering accuracy, and regular commissioning offering the biggest performance gains.
  

The built environment is under increasing pressure to use less energy, cut carbon output, and prove how well buildings perform in practice. In response, more organisations in the UK are adopting NABERS - a performance-based rating system that delivers transparent, dependable assessments of how a building actually runs.

Originally developed in Australia and adapted for the UK, NABERS measures real-world performance over a 12-month period. It looks at verified energy consumption, carbon emissions, and water usage, providing a rating based on how the building truly performs.

For data centres, where uptime, power density, and cooling loads create distinct operational pressures, NABERS provides a consistent framework for facilities to benchmark efficiency, demonstrate sustainability progress, and highlight where improvements can be made.

In this article, we examine the NABERS scheme, explore how to improve a NABERS score, and answer some common questions, including “what is NABERS?” and “what is a NABERS rating?” We also explain whether it is required in the UK, and show how RED helps organisations turn these insights into real improvements in efficiency, sustainability, and performance for data centres and other complex buildings.

WHAT IS NABERS UK?

What does NABERS stand for? NABERS (the National Australian Built Environment Rating System) provides a clear, independent view of how buildings perform in practice. In the UK, it has been adopted across offices, data centres, and other complex facilities, providing transparent, verifiable insight into energy use, carbon output, and water consumption.

Unlike many environmental certifications that focus on design or predicted performance, NABERS is grounded in actual metered data - data that RED turns into actionable client strategies, ensuring buildings perform efficiently and sustainably in the real world.

Our expertise has shown that this approach is the answer to how to improve NABERS scores and deliver measurable, long-term results.

How is NABERS different from BREEAM?

While BREEAM assesses sustainability at the design and construction stage and looks broadly at environmental impact, NABERS focuses solely on operational performance using 12 months of verified data. Many organisations now use both: BREEAM for design and specification quality, and NABERS to prove how well the building actually performs in use.

WHAT IS A NABERS RATING USED FOR?

NABERS provides a standardised way to measure and compare how buildings actually perform, helping organisations understand energy use, carbon output, and where improvements are possible.

NABERS UK is built around two primary assessment schemes:

NABERS ENERGY RATINGS (FOR EXISTING BUILDINGS)

• Measures actual energy use of offices over a 12-month period, expressed as a star rating from 0 to 6
• Initially focused on Base Building systems (core services like lifts, lobby lighting, and central HVAC), now includes Whole Building and Tenancy ratings
• Whole Building Rating: assesses the performance of the entire building, including all tenants and shared areas
• Tenancy Rating: assesses the performance of a single tenant’s space
• Provides benchmarks against similar buildings and highlights areas for improvement
• Ratings are assessed annually to track operational performance over time

NABERS DESIGN FOR PERFORMANCE (DfP)

• A framework for designing, building, and commissioning new offices or major refurbishments
• Ensures buildings meet a targeted NABERS Energy rating once operational
• Developers commit to a minimum 4-star rating at the design stage to close the gap between design intent and actual performance

By combining operational ratings with a robust design framework, NABERS gives organisations a clear understanding of how their buildings perform today - and what they can achieve tomorrow.

Different sectors benefit from NABERS in different ways, and this is where its value becomes most visible.

FOR OFFICE BUILDINGS, NABERS RATINGS:

• Track energy consumption, carbon emissions, and water use
• Give landlords and tenants a clear benchmark for operational performance
• Make buildings with higher ratings more attractive to tenants with sustainability targets

FOR DATA CENTRES, NABERS IS PARTICULARLY VALUABLE BECAUSE IT:

• Provides an independent, consistent measure of performance
• Supports operational efficiency improvements while maintaining uptime
• Helps demonstrate sustainability credentials to clients, investors, and regulators

OTHER USES OF NABERS INCLUDE:

• Supporting ESG reporting and disclosure
• Guiding procurement and operational decisions
• Meeting stakeholder expectations for verified environmental performance

HOW DOES THE NABERS RATING SYSTEM WORK?

NABERS uses real operational data to rate a building on a 1-6 star scale, based on how it actually performs over a full 12-month period. A score of 1 shows underperformance, while 6 indicates market-leading efficiency. 

In practice, 4 stars is a solid benchmark, and 5 or 6 stars point to exceptional efficiency and strong operational management. In the UK, investors and occupiers are increasingly expecting at least 4.5 stars for high-quality data centres.

To make comparisons fair, the system tailors its benchmark using factors such as:

• Total metered energy use - the actual electricity, gas, or fuel consumed over the year
• Building size and type - floor area measured using the Royal Institution of Chartered Surveyors’ (RICS) Net Internal Area (NIA), the standard for usable office space; non-office areas are adjusted or excluded
• Climate adjustment - postcode-specific data over 20 years ensures fair comparisons across regions
• Operating hours and occupancy - including intensity of use and after-hours activity
• Equipment density - accounting for the amount of operational plant, servers, or specialised equipment

The goal is to provide a like-for-like assessment so buildings aren’t penalised for longer hours, more occupants, or heavier equipment loads.

HOW IS A NABERS RATING CALCULATED

• A certified assessor pulls together and verifies a full year of building data, including:
• All utility consumption (electricity, gas, diesel, etc.)
• Metering and sub-metering architecture
• Floor area and usage characteristics (RICS NIA for office-like spaces; adjustments for non-office areas)
• Occupancy levels and operating hours
• Plant and equipment setup
• For data centres: Power Usage Effectiveness (PUE), cooling energy, and load profile

The assessor validates all data, checks compliance with NABERS rules, and submits the rating for third-party certification. Each rating is valid for 12 months, after which it must be renewed to maintain certification and continue demonstrating verified operational performance.

At RED, we support clients before the assessment stage by reviewing metering systems, identifying gaps in data quality, and ensuring the building is ready to achieve an accurate, optimised rating.

HOW TO CHECK NABERS RATINGS FOR COMMERCIAL BUILDINGS IN THE UK

As NABERS ratings are voluntary in the UK, organisations can choose to keep ratings private.

For ratings that are publicly available, you can check them by:

1. CIBSE Certification Online Register: Search by building name, address, owner, or rating type.
2. Ask the landlord, asset manager, or managing agent: Request the current certificate or rating report, often included in leasing packs or ESG disclosures.
3. Check marketing and ESG materials: Some owners display ratings on websites, brochures, or reports, often alongside EPC, BREEAM, or GRESB information.
4. Contact a NABERS UK Assessor or CIBSE Certification: They can confirm whether a building has been rated or direct you to an accredited assessor (subject to permissions).

These options help investors, tenants, and industry stakeholders verify performance claims and compare buildings across the market.

IS NABERS MANDATORY IN THE UK?

NABERS isn’t legally required in the UK, but we see clear market pressure driving adoption:

• Leading developers, landlords, and funds are actively using NABERS for office projects, especially in London and other major markets.
• Large property owners (major estates, REITs) are setting internal targets, such as achieving a minimum 4-4.5 star ratings across their portfolios to support ESG and net-zero goals.
• Investor expectations increasingly favour assets with verified operational performance.
• The City of London’s Planning for Sustainability SPD recently set a target of 5‑star NABERS for new office developments and 4‑star for retrofits. Developers are encouraged to commit to Design for Performance (DfP) at the planning stage, and must report if targets are not met.
• Central government consultations in 2021 signal potential mandatory operational energy disclosure, with NABERS or an equivalent preferred.
• Industry bodies such as the UK Green Building Council and Better Buildings Partnership support the shift from modelled EPCs to operational ratings.

At RED, we see these market and policy trends pointing to NABERS becoming an increasingly important benchmark for building performance. For developers, occupiers, and investors, it makes sense to approach new projects as if achieving a strong NABERS rating is the expected standard, even ahead of any legislation changes.

HOW TO GET A NABERS RATING FOR YOUR BUILDING

The NABERS rating process is clear-cut, but it’s all about the data. Taking the right steps guarantees your score reflects real-world operational performance. Here’s how it works, step by step.

• Step 1: Engage an accredited assessor
  Start with a NABERS-accredited assessor. They check the building’s readiness, including NIA measurements, meter compliance, and energy management system accuracy.
• Step 2: Gather 12 months of operational data
  Collect a full year of verified energy data (electricity, gas, on-site generation, and sub-metering) to reflect actual building performance.
• Step 3: Calculate actual Energy Use Intensity (EUI)
  The assessor works out energy use per square metre of occupied space, showing the impact of operations, schedules, and controls.
• Step 4: Establish a tailored benchmark
  NABERS creates a benchmark specific to your building, factoring in climate, operating hours, equipment density, and median energy intensity for similar buildings.
• Step 5: Compare performance to the benchmark
  The assessor plots actual energy use against the benchmark to calculate the E/B ratio, which translates into a 0-6 star rating.
• Step 6: Receive your rating and plan ahead
  The official score is valid for 12 months.

At RED, we help clients use these insights to maintain strong scores and drive continuous operational improvements throughout a facilities lifecycle.

HOW TO IMPROVE NABERS RATINGS

Improving a NABERS rating starts with understanding how energy is used and spotting opportunities to optimise performance. For many buildings, cooling systems offer the biggest gains - upgrading equipment, refining control strategies, and using hot aisle/cold aisle containment can cut energy use without affecting comfort or output.

Detailed energy metering is another critical factor: sub-metering makes it easier to pinpoint inefficiencies and target improvements, while upgrading plant and equipment also drives results - although it usually requires investment.

For a deeper look at the strategies that sit behind these improvements, see our guide to decarbonisation.

For data centres, operational management is particularly important. Improving PUE, optimising cooling strategies, and ensuring that IT equipment is running efficiently all contribute to a better NABERS score. Regular commissioning and maintenance keep systems performing efficiently and support continuous improvement.

HOW RED CAN HELP IMPROVE OR ACHIEVE A NABERS RATING

At RED, we bring deep technical expertise to help data centres achieve and improve NABERS ratings, ensuring performance, efficiency, and sustainability are aligned. 

Where computing loads are high, and efficiency really matters, RED’s power, cooling and MEP expertise keeps facilities running smoothly, efficiently, and with room to scale. By combining independent verification with technical insight, we help data centres turn NABERS into stronger performance and stronger market credibility.

To find out how RED can help your facility achieve a strong NABERS rating, get in touch with our team today.