On the basis of experimental investigations carried out in natural conditions this article gives: one of the possible schemes of mathematical model of solar electrolysis plant for the production of hydrogen and oxygen from water under pressure. the block-scheme of solar electrolysis plant; the software that is prepared in the Fortran algorithmic language for practical application in a computer; and also the results of calculation in a computer at the plant-operating regime under pressures P = 0.1 and 0.4 MPa. (C) 2001 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.