I got a P3 Kill A Watt as Christmas present. Besides being able to measure voltage, current and kilo-watt-hours, it can measure power factor as well.
As we know, the power factor of a purely resistive AC circuit is 1.0. Typical household electronics contain inductive or capacitive elements and thus have a non-zero phase angle between the current and voltage. This non-zero phase angle results in a power factor less than 1.0.
To improve power transmission efficiency, we would like to have the collective loads to appear as close to purely resistive as possible. If the power factor of the loads is significantly less than 1.0 then significant amount of energy is wasted during power transmission due to power line resistance.
So as a curiosity, I decided to measure the power factors of a few compact fluorescent lamps. Since one of the primary reasons people chose to use CFL’s is to save electricity, I had expected that the power factor of these CFL’s to be relatively high. But to my surprise, typical CFL’s found common in Home Depot and Walmart have rather low power efficiencies. For the CFLs I measured (ranging from 10W to 40W) they all have a power factor of just above 60%.
Clearly, more energy could be saved if the power factor of these CFLs are higher. But manufactures see no need of adding cost to their final products by adding power factor correction circuitry. After all, typical consumers only care about how much electricity they can save. Whether the power factor is 0.6 or 0.8 it doesn’t matter as the savings are pretty much the same regardless of the power factor. As for the environment it is a totally different story: the higher the power factor, the less energy it is wasted during power transmission and thus the better it is for the environment.
