Water Heating/Laundry
For Your Home
Dish Washing
A relatively common assumption is that washing dishes by hand saves hot water. However, washing dishes by hand several times a day could be more expensive than operating some automatic dishwashers. If properly used, an efficient dishwasher can consume less energy than washing dishes by hand, particularly when you operate the dishwasher only with full loads.

Dishwasher The biggest cost of operating a dishwasher comes from the energy required to heat the water before it ever makes it to the machine. Heating water for an automatic dishwasher can represent about 80% of the energy required to run this appliance. Average dishwashers use 8 to 14 gallons (30.3 to 53 liters) of water for a complete wash cycle and require a water temperature of 140 degrees F (60 degrees C) for optimum cleaning.

But setting your water heater so high could result in excessive standby heat loss. This type of heat loss occurs because water is constantly heated in the storage tank, even when no hot water is used. Furthermore, a water heater temperature of 120 degrees F (48.9 degrees C) is sufficient for other uses of hot water in the home.

The question, then, is must you give up effective cleaning for hot-water energy savings? The answer is no. A "booster" heater can increase the temperature of the water entering the dishwasher to the 140 degrees F recommended for cleaning. Some dishwashers have built-in boosters that will automatically raise the water temperature, while others require manual selection before the wash cycle begins. A booster heater can add about $30 to the cost of a new dishwasher, but it should pay for itself in water-heating energy savings in about a year if you also lower your water heater temperature. Most dishwasher booster heaters can raise the water temperature at least 20 degrees for less than it costs to keep the water heater temperature that high. Reducing the water heater temperature is not advisable, however, if your dishwasher does not have a booster heater.

Another feature that reduces hot-water use in dishwashers is the availability of cycle selections. Shorter cycles require less water, thereby reducing the energy cost. The most efficient dishwasher currently on the market can cost half as much to operate as the least efficient model. If you are planning to purchase a new dishwasher, check the EnergyGuide labels and compare the approximate yearly energy costs among brands.

Dishwashers fall into one of two categories: compact capacity or standard capacity. Although compact-capacity dishwashers may appear to be more energy efficient, they hold fewer dishes and may force you to use the appliance more frequently than you would use a standard-capacity model. In this case, your energy costs could be higher than with the standard-capacity dishwasher.


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