In the Mediterranean region, there are many drip irrigation systems with pumps that are powered by diesel generator sets (gensets). Although they could be powered by renewable energy produced on-site, technical and economic factors make that difficult. Moreover, the seasonal nature of demand requires an oversizing of energy generation and/or storage, increasing system costs. In this paper, we sought renewable energy systems that were economically optimal. We focused on six farming facility case studies to find the optimal energy generation solution using a simulation and optimization tool based on genetic algorithms. Photovoltaic-diesel hybrids and diesel systems were found to be optimal, with energy costs from 0.13 to 1.08 €/kWh and from 0.32 to 0.52 €/kWh, respectively. The strong effect of demand management was an interesting finding, as it may indicate significant system size and cost reductions. In addition, the optimum photovoltaic fixed tilt angles depended not only on the seasonal profile of the demand, but also on the pumping schedule. Although the difference between market interest rates and the rise of fuel prices strongly influences the advantage of incorporating, or not, renewable generation, this study supports that hybrid photovoltaic-diesel systems can make profitable use of renewable energy in drip irrigation.