This study presents an overview of the washing up behaviour of consumers in the UK. Peoples' individual attitudes were observed as were the amount of water and energy used, the time taken and the cleaning performance. Additionally, manual dishwashing was compared with the use of automatic dishwashers. Participants were recruited to represent all geographic regions of the UK as well as forming a representative cross-section of the population. Each of the 150 participants washed a full load of soiled tableware based on the standard EN 50242 ‘Electric Dishwashers for Household Use – Methods for Measuring the Performance’. For comparison, the best selling dishwasher in the UK in 2007 was tested under the same conditions as those in the consumer trial. Additionally, consumers who owned a full-size dishwasher were asked to load it to the point when they decided that the dishwasher was full.
The study shows that these consumers, on average, used 49 l of water and 1.7 kWh of energy, whereas the dishwasher used 13 l of water and 1.3 kWh of energy on average for the same amount of dishes under the conditions tested. Statistical analysis showed that these differences are significant. The dishes washed by hand were found to be slightly less clean than dishes washed in a dishwasher. For washing a full dishwasher load by hand, the participants needed, on average, 60 min, while they only took 9 min on average to load and unload the same amount of dishes in a dishwasher. The average participants were able to fill almost the full load into the dishwasher (96% of the items as used in a test following EN 50242).