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Green Building Sourcebook

Appliances

Appliances such as refrigerators, dishwashers, and clothes washers consume variable amounts of energy depending upon size, model, and usage patterns. Great strides have been made in the past decade to increase efficiency of appliances. To ensure that you get the most efficient model, look for products that are certified as Energy Star. The Energy Star program certifies products that are 10-15% more efficient than standard products.

However, products that do not have the Energy Star rating still may provide added efficiency, with little added cost. All manufacturers are required to post energy guidelines on a yellow EnergyGuide label, which provides estimated energy consumption and estimated costs.

Refrigerators

Refrigerators have become much more efficient over the years. For example, today a typical refrigerator with automatic defrost and a top-mounted freezer uses less than 500 kWh per year, whereas a typical model sold in 1973 used over 1,800 kWh per year. Bottom freezer models use even less energy than top freezer models, both of which are more efficient than side-by-side models. Automatic ice-makers and through-the-door water systems add cost to the refrigerator and expend additional energy. The most energy efficient models are in the 16-20 cubic foot sizes. (Sources: City of Austin Sustainable Building Sourcebook, American Council for an Energy-Efficient Economy Top Rated Energy-Efficient Appliances, Energy Star)

Clothes washers

Front loading horizontal axis clothes washers are 50% more efficient, both in water and energy use, than top loaders with a vertical axis. This is because horizontal axis machines have a higher spin speed, requiring less drying time. As with other appliances, the level of energy efficiency largely depends on usage habits of consumers. For example, consumers should use cold water cycles when possible, and only operate clothes washers with a full load (to diminish frequency of use). When choosing a clothes washer, consider the Modified Energy Factor (MEF) and Water Factor (WF). The higher the MEF, the more efficient the washer, and the lower the WF, the less water used by the machine.

(Sources: City of Austin Sustainable Building Sourcebook, American Council for an Energy-Efficient Economy Top Rated Energy-Efficient Appliances, Energy Star)

Dishwashers

As with other appliances, much of what determines the energy efficiency of a dishwasher is based upon the consumer’s habits and choice of settings, which are available on most new dishwashers. Many dishwashers now use booster heaters, which can allow the remainder of the cycle to operate at lower temperatures. Also, no-heat or air-dry settings will save considerable energy during the dry cycle. A good water saving dishwasher will use seven gallons per load on regular cycles. You can further conserve water and energy by only using a dishwasher when it is at full capacity.

(Sources: American Council for an Energy-Efficient Economy Top Rated Energy-Efficient Appliances, Energy Star)

U.S. Department of Energy

How to Buy an Energy-Efficient Dishwasher

Efficiency Recommendation
Product Type	Recommended		Best Available
	kWh/yr^a	Energy Factor^b	kWh/yr^a	Energy Factor^b
Standard Dishwasher^c	555 or less	0.58 or more	277 or more	1.16 or more

^a Based on 322 wash cycles per year, where one cycle is one normal operation with a fully loaded machine.
^b Energy factor is the inverse of the power consumption (in kWh) for one full wash cycle.
^c This recommendation does not cover compact models.

Cost-Effectiveness Example
Performance	Base Model^a	Recommended Level	Best Available
Energy Factor	0.46	0.58	1.16
Annual Energy Use	700 kWh	555 kWh	277 kWh
With Electric Water Heating
Annual Energy Cost	$42	$33	$17
Lifetime Energy Cost^b	$400	$320	$160
Lifetime Energy Cost Savings	—	$80	$240
With Gas Water Heating
Annual Energy Cost	$21	$18	$8
Lifetime Energy Cost^b	$220	$170	$90
Lifetime Energy Cost Savings	—	$50	$130

^a The efficiency (energy factor) of the base model is just sufficient to meet current U.S. DOE national appliance standards.
^b Lifetime energy cost is the sum of the discounted value of annual energy costs based on average usage and an assumed dishwasher life of 13 years. Future energy price trends and a discount rate of 3.4% are based on Federal guidelines (effective from April 2000 to March 2001).