demand for electricity in winter,much higher taht of summer,varies between 45000 at 9pm and 3000 units at 6 am
主语是demand for electricity in winter
定语是much higher that of summer,相当于which is much higher that of summer
谓语是varies
后面的between 45000 at 9pm and 3000 units at 6 am应该是状语,修饰前面的varies,表示是从……到……这个区间变化
具体是什么状语不是很肯定,不知道算不算是方式状语.