600 watt HPS light is drawing more than 600 watts

I got this great new little device similar to the one here (just a different brand)

http://michaelbluejay.com/electricity/measure.html

According to this device, my 600 watt hps light actually sucks around 700 watts from the wall socket. Is this normal?

This thing is great. I can calculate exactly how much power my grow room is going to suck and how much it is going to cost using my power companies kW/h amount.

I was surprised to realise how little power oscilating fans require. I have an average size one in there now moving air around and it only sucks 13 watts. This works out to be $1.66 a month to run 24 hours a day.

I was also pleasantly surprised after measuring my new grunty prima klima 2 speed fan too. I was worried it would suck the power given how much air it moves, but it turns out that it only sucks about 52watts (60w on the higher speed - which i thought was strange - i was expecting higher). That works out to cost me about $7.67 a month (assuming 60 watts).

My entire grow only uses about 780 watts, then drops by 700watts when the light is out which as of today is down to 12 hours from 16.

I don't think there is anything wrong. If your meter shows realtime usage you should see a spike on start-up then it should even out. It is not uncommon for an appliance to pull more or less wattage than it is rated.

I always calc. out my grow and figure out electricity cost. Its part of the fun of setting up the growroom

Will be ordering one soon, nice inexpensive tool to try to efficiently use all energy. Also useful to help hide those power surges

check it right when the lights come on and again toward the end of the light cycle.

i think the ballast uses a bunch of electricity at the beginning of its cucle and stores it up the releases it slowly.

i might be wrong and i know i worded this kinda weird but i just woke up lol