An economic analysis of the profitability of adopting solar photovoltaic energy systems for crop irrigation is undertaken. The economic, technological, and political uncertainties surrounding adoption are discussed with reference to their impact on anticipated profitability. On the assumption that the costs of producing photovoltaic modules follows a learning curve characteristic of other inventions, solar systems are likely to be viable for irrigation in some states by mid to late 1980s. A field test in Nebraska is described. (KEY TERMS: irrigation; energy; technological diffusion.) 'Paper No. 781 36 of the Water Resources Bulletin. Discussions are open until June 1, 1980.