The study on modern microgrids implicitly comes with the concern of quality of power and its impact on the electrical network. That is the result of the accumulated impact of nonlinear processes, many of which include switching elements. To perform microgrid studies, especially simulations which test smart control techniques and strategies, the ideal of sinusoidal AC waveforms is no more a valid assumption and the harmonic components must be correctly represented. This paper intends to present voltage and current signals based lumped models of harmonic electrical loads suitable for a simulation environment. The corresponding computations required for harmonic powers of the load are also presented. The calculations done could be used to obtain quantitative estimation of harmonics in contexts such as large built-environments, or microgrids with significant nonlinear processes such as chemical loads.