If you need to use them, run them a little higher than normal. Should work out well, but understand you are spending almost twice as much on electricity an hour than you'd need to. Maybe your frags would grow twice as fast and offset the cost? 2x 400W = 800W. That's almost an entire Kilowatt per hour of run time. Here at my house I'm locked in for 5 years at $0.145 per KWH. So running that would cost you nearly $115 a day @8 hours or would add $35 a month to your electric bill (That's what my lighting costs me for my 75g as with my actinics I have nearly 800W.)