The effect of the tilt angle on design aspects and performance characteristics of a photovoltaic (PV) array is examined. It is shown that a load dependent seasonal variation of the tilt angle results in a substantial increase in the generated energy, as well as a more economical design of stand-alone PV systems. The proposed algorithms for estimating the optimum tilt angle, under a variety of conditions, are general in their applicability, simple in their implementation and computationally efficient while keeping the input data requirements to a minimum. It is assumed that the array modules are facing true south.