To accurately position an object with an actuator that exhibits load dependent hysteresis requires a hysteresis model that is capable of adjusting to a change in load. In this paper we investigate the specific problem of modeling the hysteresis of a simple shape memory alloy wire that is operated under changing tensile loads. A Preisach operator that incorporates load dependent parameters in the Preisach density function is proposed as the hysteresis model. In support of this selection, a relationship between the Preisach density function and the wire's thermal coefficient of expansion is established. It is then shown that the load dependent Austenite-Martensite transition temperatures of the wire can be used to estimate the parameters of the density function. Based on these findings a load dependent Preisach operator is defined. To test this approach, a bivariate density function that incorporates two load dependent parameters is substituted for the Preisach density function. Two load dependent linear estimators are developed from experimental data and used to estimate the parameters of the density function. These estimators and the load dependent Preisach operator are then used to estimate the length of a SMA wire that is operated under several tensile loads. The estimates are compared to experimental data and a discussion of the effectiveness of this approach is given.