Is apparent/real power relevant in power consumption for LED night lights?

Discussion in 'General Electronics Chat' started by baysidedweller, Aug 22, 2014.

  1. baysidedweller

    Thread Starter New Member

    Aug 22, 2014
    I just purchased some LED night lights thinking they will save me money in the long run.
    Turns out 3 different brands I purchased were using more energy than stated (10X greater than the specification).
    One of the night lights in question has 0.6W stamped on it but in fact it was using close to 6W. On top of that, the energy consumption is on 24/7 regardless whether the light is on or not. So it is using more energy than the regular incandescent light bulbs since from my testing, they draw close to zero energy when the light is off.
    I used a fluke 23 connected to the 300mA and the ground to do the testing.
    I contacted the distributor/manufacturer and was told the method I was using was not correct.
    The exact response is as follows:
    "The equipment and the method you used to measure can only result in
    apparent power. The marking on our product is of real power which is the product of the apparent power and the power factor that your equipment doesn't seem to be able to measure. The power factor in this case is about 0.077."
    I then contacted my electric supplier, Pacific Gas and Electric and talked to one of their engineer. I was told my method was correct and I am paying the 5W and not the 0.5W.
    Since I only tested 3 different models and there are hundred of thousands night light out there, how can I prevent these unscrupulous manufacturers from selling their products with false specifications stamped on them?
  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
    In my country individual consumers pay only for real power, not for apparent. Only commercial customers pay for it.
    As for the LED bulb. I once measure one rated 230V/0.6W using power meter (hioki hitester 3333). And the result was 0.6W and 5.2VA apparent power and PF = 0.11.
  3. crutschow


    Mar 14, 2008
    The PG&E engineer was in error. Residential customers do not pay for apparent power, they only pay for real power.

    The LED lights likely use a capacitor in series to limit the current, which creates a large amount of reactive leading current. But the power company likes that since it corrects for the lagging current that most appliances create.

    If want to measure real power then you can use a power meter such as the Kill A Watt device.