The most ideal site for wind energy production is the area where moderate and continuous or steady-state wind conditions are dominant over a significant percentage of a given period of time. This paper is mainly concerned with wind speed persistence, which is an important factor in maintaining wind energy production. For this purpose, a theoretical ideal speed duration curve is proposed for determining the wind speed persistence over a given area. Errors between the speed duration curve and the theoretical ideal speed duration curve are considered as a criterion for the wind speed persistence.