Selecting an energy-efficient hot water system is crucial for Australian homeowners seeking to save on electricity and gas while reducing environmental footprints. However, the alphabet soup of star ratings, COP numbers, and various metrics used to measure water heater efficiency can bewilder consumers.

This straightforward guide is a handy reference to demystify the meanings behind efficiency scores. We’ll clarify the predominant ratings applied to systems across gas, electric, solar and heat pump models in clear terms. You’ll learn how to interpret stars, coefficients of performance, energy factors and more when comparing new purchases. Most importantly, understand why higher ratings directly translate into lower utility bills and smaller carbon impacts for your home.

With insight into what’s behind those numbers, efficiently powering your water heating needs becomes a simpler equation. Let us help you make an informed, money-saving decision for your next hot water appliance and provide daily tips for maximising efficiency.

Common Efficiency Ratings Used in Australia

The two main ratings used to measure hot water system efficiency in Australia are:

Star Ratings

The predominant rating shows a system’s energy performance based on actual testing. Electric and gas storage tank systems range from 1 to 6 stars, while heat pump and solar systems typically span 5 to 7 stars.

Coefficients of Performance (COP)

Indicates efficiency for heat pump hot water systems only. The higher the COP, the more efficient the system. COPs usually range from 2.5 to 5.5.

Reviewing these ratings when comparing systems allows you to gauge how effectively they convert energy into heat for the power consumed. The higher the star rating or COP, the more economical the system is to run.


Types of Hot Water Systems and Their Ratings

There are several types of hot water systems, each with different efficiency ratings:

Gas Storage Systems

Conventional gas hot water tanks carry star ratings ranging from just 1 star for basic models and up to 4.5 stars for the most efficient gas storage tanks.

Electric Storage Heaters

Tank-style electric systems see star ratings spanning 2 stars for entry models up to 5 stars for premium efficiency electric storage units.

Heat Pump Systems

Utilising heat absorption technology, electric heat pump water heaters achieve excellent efficiency with star ratings from 5 to 6 stars. Their COPs range from 3.0 to 5.5.

Solar Hot Water

Solar systems harness the sun’s renewable energy for zero emissions and stellar efficiency. Star ratings reach as high as 7 for evacuated tube models.

How Efficiency Ratings Affect Your Energy Bills


Your hot water system’s star rating significantly impacts running costs and environmental footprint. Systems boasting higher star ratings convert more of the energy they consume into usable heat. This greater energy efficiency means increased savings on your utility bills over time.

For example, upgrading from a 3-star gas storage heater to a 5-star gas instantaneous model saves a typical Aussie household around $180 per year on gas bills.

With solar or heat pump electric systems gaining over 2 additional stars, yearly savings can surpass $300 annually thanks to renewable energy and heat transfer optimisation.

While the upfront cost is higher for 5, 6, or 7-star rating systems, the long-term savings on energy are substantial. Doing a full cost comparison accounting for the purchase price plus lifetime running expenses helps determine which system offers the best investment.

Factors That Impact Efficiency Ratings


Various factors can impact the efficiency of your hot water system, including:

Insulation and Heat Loss

A well-insulated system reduces heat loss, retaining heat for longer periods, which can significantly improve efficiency.

Installation Quality and Location

Proper installation by a professional is crucial for maintaining the integrity of a water heater’s efficiency rating. Also, the unit’s location can affect its performance, as external temperatures can influence heat retention.

Maintenance and System Longevity

Regular maintenance can help sustain the efficiency rating of your water heater. Over time, neglect can lead to decreased performance and increased costs.

Size of the Hot Water System

Choosing the right size for your household needs is vital. An oversized or undersized system can lead to inefficiency and wasted energy.

Maximising Your Hot Water System’s Efficiency


Beyond choosing a system with a high-efficiency rating, there are steps you can take to maximise efficiency:

  • Regularly maintain your hot water system to ensure it operates at peak performance.
  • Insulate your hot water storage tank and pipes to reduce heat loss.
  • Install low-flow fixtures to reduce hot water use without sacrificing comfort.
  • Consider a timer or smart system that learns your schedule and adjusts heating accordingly.

Stay Energy-Efficient With The Right Water Heater

Understanding hot water system efficiency ratings is essential when selecting a new system. It can be the difference between soaring utility bills and significant savings. For Brisbane homeowners, making the right choice can be made easier with expert advice from The Brisbane Plumbers.

If you’re considering a new hot water system or seeking ways to improve your current one’s efficiency, The Brisbane Plumbers will guide you. Our team can help you understand the ratings and select your home’s most suitable, efficient, cost-effective hot water system. With our expertise, you can enjoy the comfort of hot water without the stress of high energy bills.

Contact The Brisbane Plumbers today to ensure your hot water system is as efficient and effective as possible. Let us help you make an informed decision that benefits your wallet and the environment.