The objective of this paper is to present a new estimator of both irradiance and temperature, called GT Estimator (G - Irradiation and T - temperature). This estimator uses the measurements of current and voltage of the photovoltaic (PV) module. The estimator eliminates the use of costly sensors for measuring the irradiance and maintains an acceptable accuracy. The equations and the algorithm for the calculation of the estimates are presented along with simulation results. (C) 2014 Elsevier Ltd. All rights reserved.