The Turgo turbine is a relatively cheap, reliable and sustainable type of impulse turbine used in hydroelectric plants, which is generally suited for medium and high head applications. Nowadays, the development and use of technologies for harnessing very low-head water resources have become highly widespread due to the low negative impact generated on the environment. Additionally, the implementation of small innovative water-related projects can be an economical option for the generation of renewable energy in developing countries. Therefore, a low-cost Turgo turbine for low-head applications was designed and manufactured for evaluating the effects of several geometric parameters involved in the design and, subsequently, in the turbine efficiency. Among these parameters, the nozzle diameter, the number of nozzles and the jet impact location were studied. For this purpose, the response surface methodology based on a Box-Behnken design of experiments was used to determine the optimal operating conditions of the referred geometric factors aiming at the maximization of the turbine efficiency, as well as to investigate the effect of each parameter on the turbine efficiency. From the experimental design, a second-order regression model was generated, which was validated. The obtained findings indicated that the nozzle diameter had a considerable influence on the turbine efficiency in comparison with the other evaluated factors. Moreover, the results showed that the maximal experimental turbine efficiency was equal to 93.7% under optimal design conditions; i.e., when the nozzle diameter, number of nozzles and the jet impact location were equal to 16.685 mm, 2 and 60 mm, respectively. Therefore, the designed Turgo turbine reported a high efficiency, which could be used for the distributed power generation.