How are refrigerator star ratings calculated?

Comparative energy consumption CEC

The energy consumption of a refrigerator is measured under conditions specified in an Australian Standard. Over a year, this value is known as the comparative energy consumption or CEC.

Concept of adjusted volume

The measure of energy service for a refrigerator is the volume that has to be cooled. However, freezers operate at a much colder temperature than fresh food compartments, so the volume of these compartments is "adjusted" to take account of the extra energy required to achieve this task. The energy service provide by a refrigerator or freezer is called the total adjusted volume.

Performance

To be eligible for an energy label a refrigerator has to meet a temperature operation test and a pull down test as defined in the Australian Standard. Refrigerators also have to meet the Minimum Energy Performance Standards (MEPS) requirements for minimum energy efficiency.

Base Energy Consumption BEC and Star Rating

The Base Energy Consumption defines the "1 star" line for particular products. An additional star is awarded when the CEC of the model is reduced by a defined percentage from the BEC. Energy reductions per star vary from 14% to 23% per star, depending on the refrigerator group. For example, if the energy reduction per star was 20% (as is the case for Groups 2, 3 6U and 7), then a CEC that was 0.8 of the BEC or less would achieve 2 stars. Similar, a CEC of 0.64 (0.8 x 0.8) of the BEC or less would achieve 3 stars and so on.

For refrigerators and freezers, there are a total of 9 groups which have been defined under the standard. However, to determine star ratings, a number of these groups are compared on the same basis, especially where they are performing a similar task, so there are only 5 BEC rating scales which cover all 9 refrigerator and freezer groups.

Refrigerators and freezers are a special category of product under the energy labelling program as they are also subjected to Minimum Energy Performance Standards or MEPS. The effect of the MEPS requirements for refrigerators and freezers was considered when the BEC lines were developed - in general terms the MEPS lines are approximately equal to the BEC (1 star) for most groups.

What about adaptive defrost?

Adaptive defrost is one of a number of new smart technologies for refrigerators where the appliance adjusts the frequency of automatic defrosts to match frost load on the evaporator. Adaptive defrost systems are recognised by the Australian Standard for refrigerators and freezers but at this stage a realistic test for these controls is not included in the test method. The standard assumes that at least one defrost per day will occur during normal operation, although some smart systems may have a longer time between defrosts under normal conditions of use. Adaptive defrost technologies will play a more prominent role in the next round of refrigerator and freezer MEPS scheduled for introduction in late 2004.

The detailed star rating equations are contained in the document "Equations for Appliance Star Ratings".

There is an overview of how star ratings are calculated for other products on this site.

This page last modified 28 June 2007