Product Sustainability ratings on the score tables
We have given some extra points to brands based on energy efficiency.
We used the sust-it energy efficiency comparison website. We gave an extra point to a brand if it had at least one A+++ model of dishwasher available in the UK in the top 25, ranked by energy use.
ISE also gets an extra point for making a hot-fill dishwasher model.
Marigold versus machine
One of the most detailed studies ever done on dishwashers was in 2004 by Professor Rainer Stamminger of the University of Bonn. He found that dishwashers used less water and electricity than washing by hand. On average, human washers in his study each used 103 litres of water and 2.5 kWh of water-heating energy. Even the most energy and water efficient human washers were using 30 litres and 1 kWh of energy.
By comparison, the machines he tested used 15 litres of water and 1-2 kWh of electricity.
These days, the most efficient dishwashers on the market on average use less than 10 litres of water and less than 0.74 kWh. Stop it before the drying cycle begins and you’ll use even less energy.
According to the Consumers’ Association, “The main wash programme on a full-sized dishwasher uses about 18 litres of water. That’s less than using two washing-up bowls full to clean 120 items.”
So dishwashers seem to come out top on water consumption, but they have to be full for the figures to stack up.
But the energy used for handwashing could be less than Stamminger estimated because he calculated the energy used based on electricity use. Whilst most dishwashers now, annoyingly, only have a cold fill and so have to use electricity to heat the water, many people have hot water from efficient gas condensing boilers to do their handwashing. Gas has a lower carbon footprint than electricity unless your electricity is from 100% renewable sources. So carbon savings can be made there, even more if you are using your own solar-heated water.
In addition, Rainer Stamminger did not include the embodied energy of manufacturing and transporting the dishwasher in his figures nor the materials used to make it.
Energy saving dishwashers
Although most dishwashers have an official A rating for energy efficiency, Which?’s tests of hundreds of dishwashers have found significant differences in electricity and water use. Which? Best Buy dishwashers with an Energy Saver logo are in the top 10% of all full-sized dishwashers they’ve tested for energy use and use 22% less energy than average. They currently list 7 models from Bosch and Beko. It should be noted that Which? did not review all the manufacturers on our score table.
- The quick wash programme often cuts out the drying cycle which uses an unnecessary amount of energy.
- Energy-save or eco programs may use the least amount of energy. They wash dishes at lower temperatures, so don’t need as much energy to heat the water. On average, energy-save programmes use about 20% less energy than the main programme.
- Check on the Energy Label for annual water consumption to compare models.
- Using the eco or energy-saving programme saves water, with the best dishwasher using 7 litres on an eco setting instead of 10 litres for the main programme.
- Wipe dishes, don’t soak or rinse or use a pre-rinse programme.
- Fully load your dishwasher. Avoid half-load programmes – the water saving won’t equate to half. It’s better to wait until your dishwasher is full and then select an eco or water-saving cycle.
German multinational Siemens, which has a joint venture with Bosch to make white goods, was widely reported to have announced an exit from the nuclear industry in 2011 in the wake of the Fukushima nuclear disaster in Japan and the subsequent swell of anti-nuclear feeling in Germany.
Chief executive Peter Loescher told Spiegel magazine:
“The clear positioning of German society and politics for a pullout from nuclear energy” meant that “the chapter for us is closed”.
However, today Siemens Energy still promotes its services as a supplier of nuclear power stations including one currently being built in Finland.
See detailed company information, ethical ratings and issues for all companies mentioned in this guide, by clicking on a brand name in the Score table.
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1 A good Life, Leo Hickman, Eden Project Books 2008
2 How bad are bananas?, Mike Berners-Lee, 2010 Profile Books
3 sust-it.net, viewed May 2014
4 Which? Dishwasher buying guide, May 2014
This product guide is part of a Special Report on Home Appliances. See what's in the rest of the report.