2. another said the power unit is the "W", W said that the real power, VA said that the virtual work, that there is a difference in power factor, W = VA cosθ, the cosθ is the power factor, power number of factors in the end, individual products, either as 0.6, some 0.8, the current most of the commercially available products are set at 0.7.

3. the cumulative rated capacity of each load calculate the total capacity, and instantly activate the power-load, such as paper printer, sold separately in order to activate the instant when the power consumption calculation, to avoid all the equipment caused by overloading, when activated at the same time, once the city UPS also interrupt the electricity supply cannot be sustained.