“…Cottet & Smith (Cottet and Smith, 2003) have used for this purpose the procedures by Bayes; Blum & Riedmiller (Blum and Riedmiller, 2013) predict energy demand using Gaussian processes, and Dongxiao et al (Dongxiao et al, 2010) use a support vector machine and ant colony optimization. However, the most popular models used to forecast electricity demand are ARMA / ARIMA / SARIMA models and exponential smoothing, which have been used, among others, in the works (Pappas et al, 2008;Taylor, 2003;Chen, et al, 1995;Lee and Ko, 2011;De Andrade &and da Silva, 2009;Bratu, 2012;Kasperowicz, 2014a,b) and they have been selected in this article to calculate forecasts for the Polish energy system.…”