“…There are different suggestions in the energy economics literature for dealing with the trendseasonal component (T t + s t or T t · s t ) of electricity spot prices. For instance, some authors use piecewise constant functions (or dummies) for the months (Bhanot, 2000;Fanone et al, 2012;Fleten et al, 2011;Haldrup et al, 2010;Higgs and Worthington, 2008;Knittel and Roberts, 2005;Lucia and Schwartz, 2002). Other model the seasonal pattern by sinusoidal functions or sums of sinusoidal functions of different frequencies (Bierbrauer et al, 2007;Borovkova and Permana, 2006;Cartea and Figueroa, 2005;Erlwein et al, 2010;Geman and Roncoroni, 2006;Keles et al, 2012;Lucia and Schwartz, 2002;Pilipovic, 1998;Seifert and Uhrig-Homburg, 2007;Weron, 2008), sometimes coupled with an exponentially weighted moving average (EWMA) (De Jong, 2006).…”