How are clothes dryer star ratings calculated?

Comparative energy consumption CEC

The energy consumption of a clothes dryer is measured under conditions specified in an Australian Standard. Over a year, it is assumed that the clothes dryer is used at rated capacity once per week (52 times per year). The initial moisture content of the clothes load is also defined in the standard.

Capacity

The measure of energy service for a clothes dryer is rated load capacity. This is the value declared by the manufacturer and defines the test load used in the Australian Standard for the determination of energy consumption.

Performance

To be eligible for an energy label, a clothes dryer must be able to dry a standard load in a single operation. Other requirements are a maximum clothes temperature limit of less than 130°C (to prevent scorching) and minimum efficiency requirements that are defined in the Australian Standard.

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. The energy reduction per star is 15% for clothes dryers. For example, a model that had a CEC that was 0.85 of the BEC or less would achieve 2 stars. Similar, a CEC of 0.723 (0.85 x 0.85) of the BEC or less would achieve 3 stars and so on.

For clothes dryers, timer and autosensing models are treated slightly differently: timer models are given a 10% penalty on energy (and for the subsequent calculation of the star rating) on the basis that the way timer controls are used in normal practice results in some overdrying of the clothes load. Under the standard test, timer dryers are operated until the load reaches a final moisture content of 6% while autosensing dryers are operated until they terminate their drying automatically (but at a moisture content of less than or equal to 6%), so the tested difference is usually less than 10%.

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