Energy cost

How much Will it run me to run a 400 watt hps for 12 hrs a day

for a month

Depends on how much your electric supplier charges you per kw/h, which can vary greatly.

To get a rough idea of cost to run a 400w for 12 hours per day, 12 x 400 = 4800w of electric used per day, so thats 4.8kw, then do 4.8 x your specific kw/h charge = rough cost per day, then times that by how ever many days are in that given month.

As i say this is a rough calculation, a 400w ballast pulls a bit more than 400w from the wall socket.

HTH

Common Calculators for Indoor Gardeners - Worm's Way

then press watt tab.i meant to say cost tab

Nice link agoodfriend, and theres me doing it the old fashioned way

Useless to me though as its all in us currency.