Statistics for The overall performance of a fin and tube type solar flat-plate collector depends mainly on a) meteorological parameters, b) operating parameters, and c) design parameters. The total system cost using solar flat-plate collectors is mainly the initial cost of the collector. In this study, a design methodology based on cost optimization is presented and the cost effective energy equation is obtained. The results obtained show that the cost optimal fin width and thickness are not affected by either the meteorological conditions or the operating conditions and as such the obtained geometries are valid for any operating and meteorological conditions. Design nomographs presented serve as quick and convenient design tools for cost optimal flat-plate collector design.