When you're shopping for dishwashers, you can't miss the prominent Energy Star label on the front of every appliance in the store. You notice them and you probably take the Energy Rating of the dishwasher into account before you make your decision to buy. If you're like most of us, though, you don't really know how much testing goes into dishwashers and other home appliances before they are given their Energy Star Energy Rating. There's a lot more to it than just plugging them in, running them and measuring how much electricity they consume.

The Energy Star testing procedure is different for every type of major appliance. In order for the comparative Energy Ratings of different products to be accurately gauged, they have to be put to the test under identical conditions. This is exactly what Energy Star does with dishwashers. The procedure is so exacting, in fact, that all machines are tested in identical climate conditions. The ambient air temperature is set at 20 degrees Celsius (give or take 2 degrees) and the humidity level is 60% (plus or minus 5%).

Energy Rating System

Unlike other appliances like fridges and washing machines, dishwashers are rated against a specially made and calibrated reference machine - a Miele G590 dishwasher. From this, the dishwasher's Washing Index and Drying Index are arrived at. In order to pass this test, the dishwasher's performance must exceed that of the specially constructed machine.

Energy Star tests for dishwashers have been frequently revised over the years in order to arrive at the most accurate comparative Energy Rating possible. The latest revision was in 2007, when Standby power usage was included in the calculations. While this may seem to be a minor point, some electronic goods actually use up to 12% of their annual kilowatt hours while on standby. Other recent revisions have included the addition of program times and wash and rinse cycle times in determining the overall performance and energy efficiency of dishwashers.

The tests and standards mentioned above are just the short version of all that is taken into account when Energy Star tests dishwashers. The level of soiling of the dishes, the types of dishes that are washed during the tests, the type of detergent and many other factors are also included. Without standardizing every detail, Energy Star could not arrive at fair and accurate Energy Ratings for dishwashers or any other appliances or electronic goods. 

And Finally...

What all of this means is that when you see two dishwashers side by side in the showroom, you can tell at a glance from their Energy Ratings which one is the more energy efficient. What's more, you can purchase the more efficient model with confidence, knowing that it will also perform as well or better than the model next to it, regardless of extra features. Because the most visible difference between cheaper dishwashers and more expensive models is in their features rather than their performance, the Energy Star Dishwashers Energy Rating label can help you make a more informed decision based on features, performance and energy efficiency.