This paper presents prediction of Grid Connected Photovoltaic (GCPV) power systems performance parameters towards Malaysia climate variations (solar irradiance and module temperature) by using Mathematical approach. The actual and prediction data measurement were analyzed on three types of solar cell technologies; monocrystalline, polycrystalline and thin film. Each PV array works with different types of inverters which are located at Green Energy Research Center (GERC), University of Technology MARA (UiTM) Shah Alam, Selangor. The prediction and detail analysis of electrical parameters are carried out by using MathCAD software. The results obtained show good agreement between prediction and actual data.