This work introduces an efficient procedure for measuring reactive power in single-phase systems in the presence of harmonic distortion. The measurement of reactive power is based on the application of the ADALINE network to estimate the voltage harmonics and, subsequently, to define a certain single-phase magnitude whose average value provides the reactive measurement. Two definitions of the reactive power have been considered: the reactive power of the fundamental harmonic Q1 and the well-known Budeanu reactive power QB, which is physically meaningless according to many studies. In addition, the proposed neural procedure of calculating the two reactive powers has been compared with other traditional methodologies for calculating Q, specifically, the application of FFT to voltage and current and the 90° voltage delay method. The new methodology has been applied to two laboratory case s...