by James Dulley
Engineering ConsultantNew energy-efficient dishwashers offer better cleaning, more optionsQ: My 12-year-old dishwasher is noisy and does not have many cycle options. I think it’s time to replace it. What are the important efficiency features when I compare models? Is hand washing dishes more efficient?A: The good news is, using an automatic dishwasher is typically more efficient than hand washing dishes (although if you take your time and are very miserly with water use, hand washing can be more efficient).
But your old dishwasher probably does need to be replaced because it has already survived longer than most typical dishwashers. No matter which new dishwasher you select, you can be certain it will use less electricity and hot water than your old one. The vast majority of dishwashers made today exceed the Energy Star efficiency standards. Over the life of the new dishwasher, the energy and water savings as compared to your old one can pay back its initial cost.
The majority of the cost of using a dishwasher is for the energy to heat the water. A portion of this energy is used by the home’s primary water heater, the rest by an internal heater in the dishwasher. With this in mind, if a dishwasher design consumes less water, less energy is needed to wash a load of dishes. Always compare the overall water consumption specifications for an average load cycle among the models.
Of course the most important feature is how well a washer cleans dishes. If it does not clean well, people tend to run it on the heavy cycle when normal will do, or they hand rinse the dishes first. Rinsing can use more than 10 extra gallons of water, and if hot water is used, more energy is being consumed. With a good dishwasher, a simple hand-scraping of dirty dishes should be adequate.
Top-of-the-line dishwashers offer many cycle settings to fine tune the process to the cleaning needs of the specific load. This is a nice feature, but most families can get by with three basic cycles: light, medium, and heavy (for pots and pans).
Some dishwashers also sport a two-pump design in the bottom of the tank: one small pump is used for spraying the dishes and another is used to drain the unit. Many models still use a single reversing pump which sprays in one rotation and drains in the other. Two smaller pumps require a smaller water reservoir, but the efficiency difference between one- and two-pump models has narrowed considerably.
Newer electronic controls offer greater convenience and efficiency. Hidden digital electronic controls — which typically run along the top edge of the door — look good when the door is closed, but you cannot watch the progress of the cycle and see the time left. Partially hidden controls are another option. A dishwasher I recently selected has exposed controls, which I find easier to see and use.
Newer dishwashers are also much quieter than older ones, accomplished by better motor/pump design and higher levels of insulation — both for noise reduction and for better efficiency. Layers of insulation are placed around the pump assembly and the walls of the cabinet and door. The stainless steel dishwasher I recently installed in my own home is significantly quieter and has shorter cycles.
Automatic dirt sensors measure the turbidity (cloudiness) of the water to determine when the dishes are clean and how long to run the cycles. There are several technologies to accomplish this, and they function pretty well. A filter option strains the water inside the dishwasher to remove food particles. Self-cleaning models use a grinder, but this may increase the noise level. A rinse-hold feature uses only two gallons of water to rinse the dishes if you do not plan to run the dishwasher for a long while.
And as for efficient washing by hand? I’ve tested it in my own home using a Delta spray kitchen faucet with touch control, which allows me to minimize water use when rinsing the washed dishes.
The overall energy savings when hand washing is really only realized during winter. I leave the warm sudsy water in the sink until it cools off. This heat is given off to the kitchen air, so the heating system has to run less (the same applies when taking a hot bath during cold winters). During summer, I do not hand wash dishes to reduce the heat and humidity buildup indoors. It can actually be a double loss during summer because your air conditioner has to run longer to remove the excess heat and humidity.
James Dulley is a nationally syndicated engineering consultant based in Cincinnati.
If you have a question about energy use or energy-efficient products, send it to: James Dulley, Electric Consumer, 6906 Royalgreen Drive, Cincinnati, OH 45244; or visit www.dulley.com.For more informationThe following companies offer efficient dishwashers:
• Asko, 800-898-1879, www.askousa.com;
• Bosch Appliances, 800-944-2904, www.boschappliances.com;
• Dacor, 800-793-0093, www.dacor.com;
• Kitchenaid, 800-422-1230, www.kitchenaid.com;
• Miele Appliances, 800-843-7231, www.mieleusa.com.