The performance prediction of Solar Integrated Collector-Storage System (ICS) is determined in terms of generalized dimensionless grouped parameters. These dimensionless parameters are primarily a combination of physical characteristics representing thermal performance curves for solar ICS systems and include information readily available to a designer pertaining to dimensions, thermal characteristics and operating conditions. The inter-relation between these is summarised as a nomogram and helps in predicting the system performance graphically for a particular locality or it may be deduced from it by simple hand calculation. This method does not require a detailed knowledge of system parameters for predicting system performance, and an advantage of this method is that short-term performance data is used to predict long-term performance and solar fraction. A simulation model was developed using a transient one-dimensional analysis for a solar ICS system. Time-dependent heat transfer coefficients and thermophysical properties were taken in the present simulation.