Combined solar-diesel installations are currently extensively used in of autonomous power supply systems. A necessary aspect in the planning and design of such systems is the assessment of their reliability. In this study, for the reliability assessment of solar-diesel installations, it is offered to use the multi-matrix method allowing to take into account the changes in solar radiation, as well as the operating modes and failure of installation elements. Reliability calculation of an autonomous solar-diesel installation used in the remote settlement Yaylyu of Altai Republic has been made.