UPS: http://www.power-solutions.com/watts-va From the above link, I have gathered that a UPS has 2 different ratings: for apparent power (KVA) and real power (KW). The KW rating is often less than KVA rating. Can anybody tell me why those ratings are different? Is it because the peak instantaneous power resulting from a power factor of 60% would be lower than the peak power when pf=unity? Power Station: Why are power stations rated in MW and not MVA? Do they assume that the load will be purely resistive, in which case the MW rating is actually a MVA rating?