Have you ever heard the term “reactive power”? Have you ever found it reflected on your electric bill as Euros? In this post we want to clearly explain what the power factor is, the reasons why electric companies penalize customers when this factor is too low, and how to correct it.

In order to understand this concept, we’ll start by explaining that electrical circuits are governed by a law known worldwide as “Ohm’s law”. This law separates two terms: current and voltage. It also creates a relation between them:

V= I· R

Using this formula, we can also get to find the power, relating it to voltage and current:

P= V· I

As we can see, power is the result of multiplying current and voltage.  Given that the voltage supplied model to housing in Spain is always 230V (or should be), we can say that power consumption depends only on the current that each customer uses, i.e., the name of devices that are connected to the house electric circuits.

Given the formula mentioned above, in order to be able to use the power, we’ll need it to be always positive. When the power is positive it can be converted into energy and this is the only scenario where it gives users benefit. In order to have positive power, we’ll need the power factor to be 1 or very close to 1. Power factor indicates the gap between current and voltage, i.e., if the current appears before the voltage, if it’s the voltage that appears before current, or if instead they both happen at the same time (which means they are in phase). Referring now to basic math, it’s important to remember that when any negative number is multiplied by a positive one, the result obtained is always negative. However when two positive or two negative numbers multiply each other, the result obtained is always positive.

In the graphics that you can find under this paragraph, we will first expose the case in which the power factor is 1, meaning current and voltage are in phase, and then another case in which the power factor is lower, meaning that voltage and current are not in phase. Power factor is referred to as Cos (Alpha).

Reactive Power not in phase

I and V not in phase

Reactive power on phase

I and V on phase


Spanish Catalan

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