How much it will cost a month depends on how much you run it and how much your electricity costs.
12/12 ? thats 12 kw hours. (actually a bit more, closer to 13 but who is counting)
if you are charged $.10 a KWH thats a $1.20 a day or about 36 bucks every 30 days. Gotta look at your bill for exact charges and do some math.
Skip LED, go with 600w or 1kw.
Still gonna need timers, fans, carbon filter to keep the stink out of your house....