Understanding Energy Ratings When Choosing A New AC

Understanding Energy Ratings When Choosing a New Air Conditioner

Every air conditioner sold in Australia carries an Energy Rating Label, and it's there for a practical reason. The label gives you a quick, standardised way to compare running costs between models before you've spent a cent on installation.

Understanding energy ratings when choosing a new air conditioner matters because two systems can look almost identical on the showroom floor and still perform very differently once they're running in your home. A higher rated unit typically uses less electricity to deliver the same amount of cooling or heating, which adds up over a typical eight to ten year lifespan.

A few things the rating tells you at a glance:

• The number of stars, which allows quick comparison against other models of similar capacity
• The estimated annual energy consumption in kilowatt hours
• The cooling and heating capacity, so you're comparing like with like
• The model's energy efficiency relative to others in its class

How Energy Rating Systems Work

Australia's energy rating scheme for air conditioners is managed under the Greenhouse and Energy Minimum Standards (GEMS) framework, with testing standards set out in AS/NZS 3823. Manufacturers test each model in controlled laboratory conditions, measuring how much electricity it draws to produce a set amount of cooling or heating.

The results are converted into a star rating, ranging up to six stars for split systems, with some inverter models now exceeding that scale on the older ten star labels used for smaller units. The rating isn't a marketing decision made by the brand. It's based on standardised test data that every manufacturer must submit before a unit can legally go through an air conditioning installation anywhere in Australia.

Key points worth knowing:

• Ratings are specific to capacity, so a 2.5kW unit and a 7kW unit aren't judged on the same scale
• Inverter systems, which adjust compressor speed rather than switching fully on and off, generally achieve higher ratings than fixed speed models
• The label must be displayed at point of sale, whether that's in store or online

Understanding the Different Efficiency Metrics

Star ratings give you a fast comparison, but the fine print on the label carries more detail for anyone wanting a proper look at running costs. AC efficiency ratings are built from several separate figures, each telling you something slightly different about performance.

The two terms you'll see most often are:

• EER (Energy Efficiency Ratio), which measures cooling output against power input, useful for comparing performance in summer conditions
• COP (Coefficient of Performance), the equivalent measure for heating mode
• Capacity output, listed in kilowatts for both cooling and heating, which needs to suit the size of the room or building
• Annual energy consumption, an estimate based on average use patterns, handy for rough cost comparisons



Commercial buyers and builders often need to look slightly beyond the retail star rating and check these underlying figures, particularly when comparing ducted or multi-head systems where capacity and efficiency vary more widely between brands.

How Energy Rating Systems Calculate the Numbers You See

It helps to know how energy ratings are calculated, because the process explains why two units with the same star rating can still perform differently in real conditions.

Laboratories test each unit at specific temperature and humidity settings defined by the Australian Standard. The system runs through set cycles while its power draw and output are recorded. That data is then compared against a reference efficiency level for its capacity class, and the result determines where the unit sits on the star scale.

A few practical outcomes of this process:

• Testing happens under fixed conditions, so real world efficiency can vary depending on your climate, insulation and how the system is used
• Larger capacity systems are held to different reference benchmarks than smaller ones
• Updates to the standard over time mean older six star units may not match the efficiency of a current model with the same rating

How to Compare Ratings for Comfort, Efficiency and Cost

Star ratings are a starting point, not the whole story. Comparing systems properly means weighing efficiency against the size of the space, how often it will run and what you're prepared to spend upfront.

When comparing models, it helps to look at:

• Purchase price against the estimated annual running cost, since a cheaper unit isn't always cheaper over its lifespan
• Capacity matched to room size, since an undersized or oversized unit will run inefficiently regardless of its star rating
• Inverter versus fixed speed technology, particularly for spaces that need steady temperature control throughout the day
• Noise output, which matters more in bedrooms and open plan offices than the rating label suggests
• Warranty terms and access to local servicing, since ongoing maintenance affects how well a system holds its efficiency



A unit with a slightly lower star rating but the right capacity for the room can outperform a higher rated unit that's the wrong size for the job.

Common Mistakes When Reading Energy Labels

A few misunderstandings come up regularly when people are comparing units, and they're worth clearing up before you commit to a system.

• Assuming star ratings are comparable across different capacities, when they're only meaningful within the same class
• Overlooking the difference between cooling and heating star ratings, which can differ on the same unit
• Focusing only on the headline star number and skipping the annual energy consumption figure underneath it
• Forgetting that installation quality and ongoing servicing affect real world efficiency just as much as the rating itself



Taking a few extra minutes to read past the star icon usually avoids these issues altogether.

Choosing the Right System for Your Home or Business

The right system depends on the space, not just the label. A well rated new AC system installed in the wrong location, or sized incorrectly for the room, won't deliver the savings the rating suggests.

Some practical considerations for different settings:

• Homeowners upgrading an ageing system often benefit most from inverter split systems, which handle variable loads efficiently across daily use
• Retail and office spaces tend to suit ducted or multi-head systems, where zoning allows different areas to be cooled independently
• Builders and renovators should factor ductwork and insulation into the decision early, since these affect how much capacity is actually needed
• Eco-conscious buyers may want to compare inverter models against reverse cycle options, which can offer efficient heating as well as cooling

Getting the sizing calculation right, based on room dimensions, ceiling height, insulation and window exposure, matters as much as the star rating itself.

Servicing and Maintenance to Protect Long Term Efficiency

A high rating on installation day doesn't guarantee the same efficiency five years later. Filters clog, refrigerant levels drift and outdoor units collect debris, all of which push running costs up gradually without an obvious sign anything's wrong.

Routine servicing helps a system hold its rated performance over time:

• Regular filter cleaning, which restores airflow and reduces strain on the compressor
• Periodic checks of refrigerant levels and electrical connections
• Clearing outdoor condenser units of leaves, dust and debris, particularly after storm season
• Scheduling a professional service annually, which picks up minor issues before they affect running costs or comfort



An efficient system that isn't maintained will drift away from its original rating faster than most owners expect.

Get the Right Advice Before You Buy

We at Mackies help homeowners, builders and business owners across the Mid North Coast work through these decisions, from initial sizing calculations through to installation and ongoing servicing. Whether you're comparing systems for a home in Port Macquarie, a retail fit out in Coffs Harbour or a new build further inland, our air conditioning services cover advice on which capacity and rating suits your space before you commit to a purchase. Give us a call or get in touch online to arrange a quote or an on site assessment.

Working through understanding energy ratings when choosing a new air conditioner properly, with advice specific to your building and climate, tends to save more over the life of the system than chasing the highest star number alone.

Frequently Asked Questions