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Watts to Amps conversion

Ray and Susan Huff

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I know the basic formula for conversion of AC watts to amps is wattage/voltage.  However, I see several online conversion charts/tools that also have a "Power factor".  What is this (resistance?) and is it important?  Our simply assume a power factor of 1.0?

Ray and Susan Huff

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Susan, what are you trying to calculate? If your question is just a general one, the power factor is simply the ratio of power used by a system vs power delivered. If the PF is 1, you have something that is 100% efficient and there is no loss in the system. A power factor of .9 would imply that the system is 90% efficient; in other words, there is a 10% loss somewhere in the system. At least I think that is how it works 😬

Edited by Jairon
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Mostly just what 'Jairon' said . . . . . . .

When the power factor is one ( 1.0 ) the electrical load is using all the energy.

In a DC circuit ( battery for example ) all the current that flow through the load does some measurable work. PF =1.0

An AC circuit may be pure resistance PF=1.0 , like an old fashioned space heater that glows orange. Nothing tricky or weird happening there. All the electrons that flow through that resistance ( nichrome wire ) do work >> make heat & orange light and that's the end of it. 

HOWEVER, when PF < 1.0 . . . like a running a motor which generates not only obvious work but also energy stored in the form of magnetic and electric fields. The energy sometimes BOUNCES around. It can actually come into your house get stored in the motor of your air conditioned as magnetic and electrical fields and then a fraction of a second later it bounce back out of the house thru the power lines it came in on headed back toward the power station then a fraction of a second later bounce back into the house and that is happening continuously when the power fact is less than one.

WHO CARES? . . . the energy bouncing around goes thru wires and the wires have some resistance and they heat up slightly and that uses up some of the energy the power company produced to sell to you. So bouncing energy is dissipated, that is it uses up its potential to do useful work a little bit each time it bounces around. The lower the power factor the more bounces and the more wasted energy due to slight heating of every wire it passes thru. Residential users usually ignore this and power company just charges a little more to allow for the waste. HOWEVER, huge factories with big Big BiG BIG machines can generate really large amounts of wasted energy and they have to PAY FOR IT. In that case the company/factory will do electrical tricks to make the power factor of the factory be closer to 'ONE'. Tricks like adding inductors which store magnet energy or capacitors which store electric field energy and so avoid the really big bunches of energy bouncing really long distances on the power grid.


In electrical engineering, the power factor of an AC electrical power system is defined as the ratio of the real power absorbed by the load to the apparent power flowing in the circuit,

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Easy peasy - just get a: 


You will know everything you need for plug in stuff. 

Don't worry about power factor. Well - unless its a really big motor or inductive resistance. In that case 30 amps ain't doin it anyways. 

For the big stuff - its usually got a labeled power draw - but if you must,



Edited by BackofBeyond
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