In order to anticipate the need for generating capacity, utility planners must estimate the future growth in electricity demand. The need for demand forecasts is no less important for the nation's Rural Electric Cooperatives (RECs) than it is for the investor-owned utilities. The RECs serve an historically agrarian region; therefore, the irrigation sector accounts for a significant portion of some. of the Cooperative's total demand. This paper develops a model of the RECs' demand for electricity used in irrigation. The model is a simultaneous-equations system which focuses on both the short-run utilization of electricity in irrigation and the long-run determination of the number of irrigators using electricity. Irrigation demand is described by a set of equations in which the quantity of electricity demanded, the average electricity price and the number of irrigation customers are endogenous. The structural equations are estimated using pooled state-level data for the period 1962-1977. In light of the model's results, the. impacts of changes in. relative energy prices on irrigation are examined.