5.5: Clothes Washers

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Clothes washers and dryers account for 10 percent of the residential energy consumption, with most of the energy consumed for hot water used for washing.

An estimated 85% to 90% of the energy is used for heating the water.
Relatively 10% to 15% of the energy is used by the clothes washer itself to operate the motor and controls.

A typical household does nearly 400 loads of laundry a year, and each load in a conventional washer uses 40 gallons of water. Therefore, any reduction in energy consumption for clothes washing application would involve reduction in hot water use.

Types of Clothes Washers

The basic principle for cleaning clothes has remained unchanged—wet the garment, agitate it to loosen the dirt from the cloth fibers and then use more water to rinse the dirt off. What has changed over the millennia is the method of agitation. Pounding garments with stones was common for several thousand years and along the way someone also figured out that using heated water got out a lot more dirt.

Clothes washers come in two types: Horizontal axis (h-axis) or front loading and Vertical axis (v-axis) or top loading (shown in Figure 5.5.1).

Figure 5.5.1. Horizontal axis (front loading), as shown on the left, and vertical axis (top loading), as shown on the right

Most clothes washers produced for the U.S. consumer are vertical axis (v-axis) washers with a central agitator. While there are variations, most v-axis washers suspend the clothes in a tub of water for washing and rinsing.

As an alternative, the horizontal axis (h-axis) washer tumbles the wash load repeatedly through a small pool of water at the bottom of the tub to produce the needed agitation. This tends to reduce the need for both hot and cold water.

The h-axis washer, popular in Europe, has a very limited market share in the United States at present. Yet, estimates have shown that a large quantity of energy and water could be saved through the replacement of conventional v-axis washers with the h-axis design.

H-Axis Washer

H-axis or tumble-action machines repeatedly lift and drop clothes, instead of moving clothes around a central axis. H-axis washers also use sensor technology to closely control the incoming water temperature. To reduce water consumption, they spray clothes with repeated high-pressure rinses to remove soap residues rather than soaking them in a full tub of rinse water.

The following video explains how an H-axis washing machine works.

In a study conducted by Oak Ridge national Laboratory (ORNL) in 1998 for U.S. Department of Energy, it was found that, on average, the h-axis washer used 62.2 percent of the water used by the v-axis washer, and this yielded total water savings of 37.8 percent. Moreover, the average h-axis washer consumed 42.4 percent of the energy used by a typical v-axis washer in the study, resulting in energy savings of 57.6 percent.

Features of the h-axis washer include:

Auto temperature. The machine will mix hot and cold water to a preset "warm" and "cold" so that the water is warm enough for the detergent to dissolve and optimally perform. During the winter in many parts of the country, cold tap water can be too cold to wash your clothes well.
Water level settings. Some of the very high-end machines sense the amount of clothing and automatically adjust the water level, but all except the most basic machines offer at least four settings.
Capacity. If you have a large household or athletes who produce an astounding amount of laundry each week, a larger capacity machine is a must. The front loaders generally hold more because they don't have the agitator. A definite minus for the front loaders, however, is the actual loading because you have to bend over to put in the clothes. To minimize this fact, the machines and their matching dryers are often displayed in stores on a raised platform.

Energy Efficiency and Water Usage

Stricter new federal standards for clothes washers took effect in two stages. The first stage was in force as of January 2004. Then in 2007, the second stage further strengthened the standard. Three factors are used in determining the federal standards:

Energy Factor is a metric that was previously used to compare relative efficiencies of clothes washers. The higher the Energy Factor is, the more efficient the clothes washer is. For clothes washers, Energy Factor is calculated using the formula
\[ Energy \, Factor = 392 * \dfrac{Volume \, (ft^3)}{Annual \, Energy \, Use \, (KWh)} \]

Water Factor is the number of gallons per cycle per cubic foot that the clothes washer uses. The lower the water factor, the more efficient the washer is. So, if a clothes washer uses 30 gallons per cycle and has a tub volume of 3.0 cubic feet, then the water factor is 10.0. Note: the energy factor for washers does not indicate the real energy efficiency because of the tub size and other factors. Therefore, the Energy Factor is modified to include the tub size and drying characteristics.
Modified Energy Factor (MEF) is a new equation that replaced Energy Factor as a way to compare the relative efficiency of different units' clothes washers. MEF takes into account the amount of dryer energy used to remove the remaining moisture content in washed items and is calculated using
\[ MEF = \cfrac{ft^3}{\cfrac{kWh}{Cycle}} \]

Additional Information

For more information about MEF circulation, please see the August 27, 1997 Federal Register entry regarding 10 CFR Part 430.

Clothes Washers and Environmental Protection

Here are some things you can control to minimize the environmental impact of your clothes washer.

Wash full loads—Clothes washers are most efficient when operated with full loads.
Wash clothes in cold water – It will conserve energy and is also recommended for colored and many delicate fabrics.

In addition:

Consider Front loaders – Since they use less water, they use less energy. The most efficient front loaders use less than half the amount of water used in the average top loaders.
Purchase washing machines with the Energy Star designation – They are 50 percent more energy efficient than the current minimal allowable standard.

Many new energy-efficient, water-conserving clothes washers have been introduced over the past few years. These resource-efficient washers are available in a variety of sizes and configurations offering consumers a wide range of front-loading and top-loading styles in many different price ranges.