[1]sys, to the total on-site electric demand E[1]total to allcomponents, including fans, pumps, chiller, cooling tower and boi-ler; the summation is performed over all operating hours:COPsys ¼Ptimeðj Q[1]sys jÞPtimeE[1]totalð1ÞQ[1]sys ¼j Q[1]sen jþj Q[1]lat jþ m [1]