The 35 degree solution
For years I’ve had to avoid my wife, for fear that she would again ask me how long she must wait before I will replace our leaky, ineffective dishwasher. This Indesit was so old that the last few repairs have required salvaging used spares. I had been procrastinating that decision even though I knew that it would reduce wasted water and electricity. My procrastination had nothing to do with a fondness for mopping the floor or scraping crud off the bottoms of teacups. I simply feared the amount of research that would go into finding an energy-efficient, water-conserving dishwasher that gets dishes clean. I am happy to report that my new Bosch SGS44E12EU (also called the SGS43E02EU) arrived today, and the investigation was not quite as painful as I had anticipated.
Not that I got everything that I wanted. My first goal was to find a dishwasher that could make use of the spare hot water my solar panels produce for nine months of the year. Alas, a Bosch technical representative explained to me that no domestic washer has hot and cold intakes, and the intake valve on a Bosch dishwasher could not tolerate a temperature above 40 degrees. This would require me fitting an expensive mixer valve to cool the water before it entered the machine. Besides, he explained that the way modern dishwashers work is to start with cold water and gradually raise the temperature. Use hot water in the first cycle, he warned, and you will bake the food onto the plates. I gave up on that track.
The next step was to compare water and electricity usage of various dishwashers. In Europe, Australia and many other markets, this is a simple task. Each appliance is labeled with a large sticker showing energy consumption, water consumption and an overall A-G rating. Dishwashers in Europe get three ratings: one for energy consumption, one for washing efficiency and one for drying efficiency. The Department of Minerals and Energy has long been promising South Africans a similar system, starting with refrigerators in May of 2005. Two and a half years later, the only appliances with an energy labels are a few imports with their European label intact.
Still, through the Internet, brochures and the Which? website, it was possible to get information from overseas efficiency ratings. Bosch’s South African website, for example, clearly displays the European ratings and consumption data for all of its dishwashers. (Curiously, they don’t display that information for their tumble driers, which, like the vast majority of these energy hogs, get Cs.) All of Bosch’s dishwashers get European As for energy consumption, which means that they use less than 1.06 kilowatt hour for a standard 50 degree wash. Not coincidentally then, many dishwashers, including all of the Bosch dishwashers sold in SA use exactly 1.05 kWh. The one I chose also uses a modest 17 litres of water for a standard wash. The top-of-the-line SGS 46 E 28 GB uses a mere 12 litres. But it costs R6399, a full R3000 more than mine, which is a lot of money to pay to save the equivalent of less than a flush of the toilet.
More important, the upper-range dishwashers have 45 degrees as their coolest setting. The economical dishwasher I chose goes down to 35 degrees. My sister-in-law uses a Bosch similar to mine and says that she never moves it from that coolest setting. She doesn’t rinse anything before putting it into the dishwasher, and even sticky porridge bowls come out clean. I haven’t succeeded in getting the data from Bosch on the electricity consumption of a 35 degree wash, but I did my own calculations. Since it uses 1,05 kWh for a 50 degree wash, and since heating 17 litres of water by 15 degrees should theoretically require 0,28 kWh, the 35 degree wash should use approximately 0,77 of a kWh.
A while ago, I checked the consumption of my old dishwasher at home, using the same, moderately precise methods I used to check electricity lost to chargers, transformers, appliances on standby and other vampires. It used 1.35 kWh on its lowest setting and guzzled 35 litres of water. Worse yet, because it cleaned so poorly, we used many more litres rinsing dishes. This is a purchase my gardener will appreciate. (Why? See here.)
My dishwasher only gets a C for drying efficiency, but that’s because it doesn’t have the electricity-wasting drying feature. It should get an A+ for leaving that off.
If you want to read a good overview of dishwashing written with a sense of humour, check out the Appliance Advisor’s guide to green dishwashing. By the time you are finished reading it, you will be convinced never to rinse your dishes again before putting them in the machine.
But do you even need a dishwashing machine? Advertisements for dishwashers often claim that they use far less water and energy than hand washing. I’m not so sure. Washing carefully, with 5 liters of solar-heated rinse water in one sink and 10 litres of solar-heated soapy water in another, I could beat any dishwasher on energy consumption. But my new dishwasher is a big step in the right direction. And it’s a lot better for my marriage.