What does the power factor mean?

Pay close attention to the power factor

In my previous texts, I mentioned the power factor. I received questions from visitors asking me to explain what the power factor actually means. The power factor indicates the relationship between apparent power and real power. Ultimately, you pay your energy supplier for the real power you consume. The power factor shows how much electricity is actually used to create light.

In the most ideal situation, the real power is equal to the apparent power (= 1). This means no extra power is needed to make the light burn at the highest available power. In practice, it is often different. This is why many product specifications indicate the power factor. Extra power is required to deliver the desired power to the user when the power factor is less than 1.

Here’s an example. Energy costs are calculated based on power multiplied by time. When you use a 100-watt lamp, we are talking about a real power (P) of 100 watts. If this lamp is on for 10 hours, you will have consumed 10 hours x 100 watts = 1 kWh of energy. In this case, the apparent power is equal to the real power (= 1).

But what if the power factor is less than one?

It can also happen that you use more power (watts) than what is indicated on the lamp. Older LED lighting often has a power factor of only 0.6 or lower. This means you are consuming at least 40% more power. This is called reactive power. Products with a power factor of 0.9 or higher are considered good products according to this factor. Some energy suppliers are unable to detect reactive power, while LED lamps with low and high power factors are priced the same. However, you will pay much less for electricity with a lamp that has a high power factor than with one that has a low power factor.

A 10-watt LED lamp with a power factor of 0.94 consumes 6% more power. When the lamp has a power factor of 0.5, you consume 50% more power. Despite both lamps consuming 10 watts, the rest of the power is wasted. You end up paying for that.

Nowadays, more and more energy suppliers notice this. The smart meters they produce also measure reactive power, which makes choosing an LED lamp with a high power factor even more interesting. With these types of meters, you pay for both the real and the apparent power for a lamp with a low power factor. The closer to PF 1, the less you need to pay.