The aim of this study, based on measurements made at Piracicaba, in São Paulo State, Brazil, was to develop and appraise a mathematical model for evaluation of solar energy potential as a function of a single measurement of solar irradiance at solar noon. The values of solar energy potential calculated permit the evaluation of the maximum possible performance of energy capture systems, which is very important in engineering projects designed to make use of solar energy in its various forms, including capture by the biomass, photoelectricity for small potentials, direct capture by colectors, irrigation of crops, agricultural potential production, agroclimatic zoning and resources for varied thermodynamical cycles. The performance of the estimation model of maximum energy input was examined using determination coefficients (r2) and Willmott's agreement indices (d) applied to estimated and observed data on the selected days at the site studied. A new way of estimating the a and b parameters of the Angström equation is proposed, which is irrespective of daily integrations and does not require a large number of radiometric measurements, one such measurement taken at sloar noon being sufficient. The results presented show that the proposed methodology was efficient for the evaluation of the Angström equation parameters, besides eliminating the multiple error sources produced by the conventional methodology. For the climatic conditions of Piracicaba, we conclude that it is possible to estimate accurately the maximum daily solar energy input and that the estimation of the global irradiance by the proposed method generated more exact values than those obtained using measurements of the duration of bright sunshine. Keywords: global irradiance, modelling, solar radiometry, maximum flux density.