400 watts is nothing. When people get caught because of energy usage it's usually for like 20 1000-watt lights in the basement or something.

Your setup probably draws closer to 500 watts with the ballast, so assume 1 kilowatt hour will run your setup for 2 hours. A kilowatt hour of electricity usually costs 10 cents or less. If you're running 12/12, that's 60 cents a day.

A bathroom vent fan would work well, if the noise doesn't matter and if you have somewhere to vent to.
khronik Reviewed by khronik on . 400W HPS and electricity cost??? i have recently purchased a 400 watt HPS and MH from HTG with a growbright MH bulb and a agromax HPS bulb. I plan on putting it in a closet that is about 3'x5'. I am looking to see if anyone would know about how much that would run my energy bill, also if something like that in an average sized appartment would be flagged by the local authorities??? Also if anyone has any experience in the same situation i could use some temp and ventilation advice.... Rating: 5