This excerpt taken from the AYE 10-Q filed May 9, 2006.
Equivalent availability factor (EAF). The EAF measures the percentage of time that a generation unit is available to generate electricity if called upon in the marketplace. A units availability is commonly less than 100%,
primarily as a result of unplanned outages or scheduled outages for planned maintenance. Allegheny monitors EAF by individual unit, as well as by various unit groupings. One such grouping is all supercritical units. A supercritical unit utilizes steam pressure in excess of 3,200 pounds per square inch. This design characteristic enables these units to be larger and more efficient than other generation units. Alleghenys Fort Martin, Harrison, Hatfields Ferry and Pleasants generation facilities contain supercritical units. These units generally operate at high capacity for extended periods of time.