Research shows capacity of photovoltaic array can be confirmed,if generic program of optimum sizing stand-alone photovoltaic systems is adopted,and using days of storage of batteries equal to zero,at the same time the tilted angle with yields of the highest value of radiation in the month with the lowest radiation is considered as the optimum tilted angle.

The optimum tilted angle of fixed photovoltaic array toward the equator depends on the nature of loads besides the meteorological and geographical features,the characteristics of the three loads,balanced,seasonal and provisional,were studied.

In determining the optimum tilted angle of fixed arrays for a stand-alone photovoltaic power system with steady load throughout a year, the continuity, uniformity and maximum of solar radiation on the surface should be considered comprehensively.