What’s the most energy-efficient way to clean your dishes: hand-washing or using a dishwasher? While hand-washing may seem more energy efficient, it actually isn’t unless you’re very frugal with the water (or have solar-heated water). Using a dishwasher can be considerably more energy efficient if you choose your appliance intelligently. (To use the least amount of electricity, run the dishwasher only when it’s full and let the dishes air-dry.)
The most energy-consumptive part of dishwasher action is not the operation of the motor, but rather the production of heat. This includes heating the water (by the home’s water heater, as well as the dishwasher’s own booster heater) and the heat generated to dry the dishes. The less hot water you use and the less you use the dishwasher’s drying function, the smaller the model you can buy and the more energy you’ll save. Look for models that give you options, such as soil sensors and wash cycle selection.
Dishwasher efficiency standards are based on annual kWh consumption, gallons of water used per cycle, and Energy Factor, EF, which reflects the number of cycles performed per kWh. The most energy-efficient models are in CEE’s Tier 2, in which standard-sized models (those that can handle eight or more place settings) can use no more than 295 kWh per year and 4.25 gallons per cycle, and must have an EF of at least 0.75. For compact models, the limits are 222 kWh per year, 3.50 gallons per cycle, and an EF of at least 1.00.
You’ll find models that use relatively little electricity but more water, and vice versa. The choice will need to be made based on the source of your electricity and the fuel you use for water heating.
The compact dishwashers don’t tend to outperform the standard-sized machines in water use, but they use less electricity. They take up less room and a full load is quicker to come by.
Window air conditioners arrived on the scene somewhat later than electric refrigerators and clothes washers, but in hot and humid parts of the country, their usage rivals that of home heating in Minnesota. Window air conditioners are ranked according to their Energy Efficiency Ratio (EER). Higher-efficiency models have more efficient compressors, pumps and fans, and more effective heat-transfer surfaces. Interestingly enough, these don’t necessarily carry a higher price tag compared to less efficient models. Before you buy, think well about whether you even need a window air conditioner (versus the smart use of fans and window coverings, which may suffice in many climates). But if you need one, here are some of the best.
Different sizes and types of air conditioners have different federal standards for minimum EER, and the current Energy Star standard requires a model to be at least 10% more efficient than the federal standard. The playing field is very crowded around an EER of 10.8, exactly 10% over federal standards. A few models pull ahead in the 11 to 12 EER range, and a selection of models of different capacities is included in the table.
The diversity of sizes and designs is particularly great for air conditioners, and before your next purchase you will want to consult the Energy Star website directly and peruse its long list of rankings.