This experimental and theoretical study presents the performance of copper oxide (Cu2O) nanofluid in a single slope solar still fitted with an external thermoelectric condensing channel. Four thermoelectric cooling modules (TEC) are installed around the walls of the external channel in order to make a cool place in the vapor flow, and also the Cu2O water nanofluid with different volume concentrations is employed. The temperatures of glass cover, basin water, absorber plate as well as distillated water productivity, and daily energy and exergy efficiencies of the modified solar still are presented during July in Razi university of Kermanshah (Iran). Moreover, the cost of distilled water for different cases is calculated. The results disclose that the productivity, energy and exergy efficiencies of solar still equipped with the external thermoelectric condensing channel enhance by about 38.5%, 38.9% and 31.2%, respectively. In this case, by adding 0.08% volume fraction of the Cu2O nanoparticles in basin water, the productivity, energy and exergy efficiencies are enhanced about 82.4%, 81.5% and 92.6%, respectively. The cost analysis designates that in optimum mode, the cost of distillated water per liter is 0.021 $/L/m(2) for this modified solar still. (C) 2018 Elsevier Ltd. All rights reserved.