On 3/2/2017 11:45 AM, Pat wrote:
I was going to respond to the OP, but Jeff beat me to it. Switching
supplies are notorious for having very poor power factors under light
load. I looked up the specs on the kill-a-watt and it is supposed to
read power factor correctly when seeing a pure sine wave. Of course,
there is no guaranty the current waveform is a pure sine wave. It is
more likely to have spikes all over the place. (That's one of the
reasons switching supplies can cause RF noise.) My guess (and that's
all it is) is your supply is using under well under 100 watts, but
your kill-a-watt is confused by the strange current waveform and says
it is using 200 watts.


So, "maybe, maybe not" on the Kill-a-watt number. My scope is packed
away waiting for its once-a-year use or I'd look at the PSU input current.