Dishwashers carry an EU energy label which rates products from A-G for energy efficiency, cleaning performance and drying performance. The vast majority of products are at least A rated for energy. However for dishwashers the energy rating is not based on actual energy consumption but the energy efficiency in relation to the dishwasher capacity (the number of place settings the machine can wash). The bigger the dishwasher in terms of place settings the greater the energy consumption. The table below shows approximate annual running costs of A rated dishwashers of different capacities. A place setting is defined as the cutlery/crockery for 1 person for one meal i.e. plate, bowl, cup/glass, knife fork and spoon.
| Number of place settings | Energy rating | Cost per cycle | Annual running cost |
| 14 | A | 14 pence | £ 34.44 |
| 12 | A | 13 pence | £ 33.45 |
| 9 | A | 11 pence | £ 25.56 |
| 7 | A | 9 pence | £ 21.64 |
| 4 | A | 7 pence | £ 15.73 |
| Assumptions: Based on maximum energy consumption, current average energy price and an average of 250 cycles per year | |||
However it should be noted that the energy efficiency label only refers to one of the programmes offered by a dishwasher (usually to most energy efficient one) and other programmes may not deliver the same energy efficiency.
Tips for buying a dishwasher
Improvements in the energy efficiency of dishwashers in recent years means that the vast majority are A rated and so there is little to chose between them in terms of energy efficiency alone. The difference in annual running cost between an A rated machine and a B rated machine is only about £ 5 - £ 7 per year.
Smaller dishwashers use less energy per cycle but hold fewer dishes so may need to be run more often, the table below shows the costs of washing 3000 place settings using A rated dishwashers of different capacities (assuming they are all filled to capacity). 3000 place settings approximately equates to a year of washing for a typical family.
| Dishwasher capacity (place settings) | Number of cycles required for 3000 settings (1 year for a typical family) | Annual running costs |
| 14 | 214 | £ 29.87 |
| 12 | 250 | £ 33.88 |
| 9 | 333 | £ 34.52 |
| 7 | 429 | £ 37.8 |
| 4 | 750 | £ 49.87 |
The difference between a slimline 9 place setting dishwasher and a large 14 place machine are only about £ 5 per year, and the larger machines are much more expensive to buy.
What is most important is to select a dishwasher that suits your household needs and has good cleaning performance and reliability. For instance a large family should go for a 12 or 14 place setting capacity machine otherwise they will be stacking and un-stacking twice a day which is very impractical. Single people or couples will find medium or slimline machines more practical as they may need to wait 2 – 3 days to fill a large machine and so may be tempted to set it away half full.
Practicality, reliability, price and cleaning performance are more important factors than energy efficiency when purchasing a dishwasher.
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