“…Among the various forecasting models [11,12,13], due to its superiority in limited data forecasting, grey model has potential to become a very powerful tool for natural gas forecasting [14,15], in particular, the grey model of the first-order and one variable (GM(1,1)) [16]. The GM(1,1) model achieved significant improvements in prediction and simulation accuracy from the following aspects; a generating operator [17], parameter estimation [18,19], differential equations [20], non-equigap grey model [21], hybrid models [22,23,24], etc.…”