The most energy efficient 18-inch dishwasher currently on sale is the Asko D5894A, as of March 2015. It is a panel-ready dishwasher that qualifies as an Energy Star appliance according to the Department of Energy. It is estimated to consume only 187 kilowatt-hours of energy per year of use.
Asko makes several other 18-inch dishwashers that are highly energy efficient as well, but the D5894A is the most efficient of its products or of products from any manufacturer. Several other companies manufacture 18-inch dishwashers with highly competitive energy consumption as compared to the D5894A, including Bosch, Whirlpool and Danby. Most of these competing models consume between 200 and 250 kilowatt-hours of electricity per year.
On average, high-efficiency dishwashers that qualify as Energy Star high-efficiency appliances use about 5 percent less electricity than standard models. However, they are much more efficient in terms of water usage, where these appliances use 15 percent less than other models. Lower water use also leads to lower energy use, as most dishwashers depend mainly on an external water heater for hot water. The Asko D5894A improves the energy use average considerably, as it is 39 percent more efficient than the Department of Energy's standard, but it is only average in terms of water savings for efficient dishwashers at 16 percent better than the standard.