AC Transformer actual energy used

Discussion in 'General Electronics Chat' started by Ralph.norman, May 11, 2010.

  1. Ralph.norman

    Thread Starter New Member

    May 11, 2010
    This is probably the proverbial stupid question, but here goes...

    I have an AC transformer for landscape lighting.

    110v AC in --to-- 12v AC out.

    The transformer is rated to support a load of up to 300 watts.

    My total load is 150 watts (15 10-watt bulbs)

    QUESTION: When the transformer is turned on, does my electric meter see me as using (and of course paying for) 300 watts (rating), 150 watts (actual load), or somthing else?
  2. Wendy


    Mar 24, 2008
    Your electric meter sees all, charges for all.

    And it measures in KiloWattHours, so it will measure the lights.

    The good news is a transformer is one of the simplest and most efficient electric components invented by man, unlike your lights. Figure about 5% is going to light, the rest is wasted heat. There are reasons LEDs are taking over.
  3. Ralph.norman

    Thread Starter New Member

    May 11, 2010
    So in one hour I use 150 watt-hours of electricity and NOT 300 watt hours (in this example).

    Your comment is spot on as I am considering replacing the incandescent lights with LEDs at approximately 10-20% of the energy requirement for a slightly higher number of lumens of light.