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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 following formula:

$$\text{EnergyFactor}=\text{}392\text{}\times \text{Volume}\left({\text{ft}}^{\text{3}}\right)\text{}/\text{AnnualEnergyUse}\left(\text{KWh}\right)$$

**Water Facto**r 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.

$${\text{MEF=ft}}^{\text{3}}\text{/KWh/Cycle}$$

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