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The authors conducted a study of washing machines in order to provide customers with more accurate information in regards to their purchases. In this research, the same laundry washing load was washed by four different types of washing machines, two with vortex systems and another two with drum systems. For each machine, the authors used the standard washing course and measured the amount of water and electricity used. Before washing, Japanese Industrial Standard (JIS) soiled cloths, small‐sized modified mechanical action (MA) test cloths developed by the Danish Technological Institute (DTI) and small‐sized Eidgenossiche Materials Purufungs Anstalt 306 (EMPA 306) were stitched to the same position on the sample laundry. After washing it, the authors analysed the reflectance of the JIS soiled cloth and the difference of Kubelka‐Munk equation (K/S) values before washing and after washing (from this, the authors estimated the decreased soil amount). They also measured the MA by one‐fifth of the DTI MA values (MA/5‐value), and the number of dots removed during the washing cycle. As for washing performance, the authors detected the level of detergency and the MA from the following parameters. They compared the washing performance of the four different washing machines by the K/S‐value per unit of water consumption and per unit of electricity consumption. The results showed almost the same level of washing performance amongst the four machines. However, there were differences in the amount of soil removed per litre of water consumption [the vortex (beat) type was the most efficient]. There were also differences in the amount of soil removed per minute of washing time and per Wh of electricity consumption. Upon both of these parameters, the vortex type washing machine was the most efficient. It is expected that these results will be helpful to consumers when choosing a new washing machine.

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