Two SIS methods, called SIS1 and SIS2, are proposed in Ref. [17]. From a biased density, *q*, SIS1 independently samples *M* different wind speeds, *x*_{i}, $i=1,\u2026,M$. Then, it runs the simulator *N*_{i} times at each sampled *x*_{i}, $i=1,\u2026,M$, where *N*_{i} is called an allocation size. Figure 1 depicts the overall procedure of SIS1. Let $Yj(i),\u2009i=1,\u2026,M,\u2009j=1,\u2026,Ni$, denote the load output obtained in the $jth$ run at the input wind speed, *x*_{i}. With these outputs, the POE estimate of SIS1 is