Abstract This paper presents a modified current–voltage relationship for the single-diode model. The single-diode model has been derived from the well-known equivalent circuit for a single photovoltaic (PV) cell. A cell is defined as the semiconductor device that converts sunlight into electricity. A PV module refers to a number of cells connected in series and in a PV array, modules are connected in series and in parallel. The modification presented in this paper accounts for both parallel and series connections in an array. Derivation of the modified current–voltage relationships begins with a single solar cell and is expanded to a PV module and finally an array. Development of the modified current–voltage relationship was based on a five-parameter model, which requires data typically available from the manufacturer. The model accurately predicts voltage–current (V–I) curves, power–voltage (P–V) curves, maximum power point values, short-circuit current and open-circuit voltage across a range of irradiation levels and cell temperatures. The versatility of the model lies in its accurate prediction of the aforementioned criteria for panels of different types, including monocrystalline and polycrystalline silicon. The model is flexible in the sense that it can be applied to PV arrays of any size, as well as in simulation programs such as EMTDC/PSCAD and MatLab/Simulink. Accuracy of the model was validated through a series of experiments performed outdoors for different configurations of a PV array.