Hi, I did alot of googling and tried to search every forum I could, but I didn't quite found what I was looking for. Sorry if this has been asked before, english isn't my first language so there's a chance that I used wrong words to search for this question. Also I'm not sure if you use the same type of symbols that we use in Finland for electrical engineering. I will try to explain them if I can =) Okay to the problem in hand. I am an electrical engineering student, I have studied for 2 years. We had many instances that we had to calculate power factors (symbol that I used is "cos(phi)" and apparent powers (symbol that I used is "S") that the main transformer "sees" in the secondary side. Here is a picture that I hope clarifies the problem: http://postimg.org/image/jozu0g543/ Then the question, I have always calculated all the different active- ("P") and reactive ("Q") powers and taken the square of their sums power to get the apparent power ("S"). Equation S = sqrt((sum P)^2 + (sum Q)^2). And from that I have calculated the power factor. Is there a faster/smarter way of doing this? The way I have been using isn't a problem if you are using under 10 outputs but after that it is quite laborious! Thanks for your input, and sorry for the long "question", also for my English!