OK if you guys want to know how much you will be paying to the power company or how much your power bill will change here is how to figure it out. I am a ELECTRICAN and we use this formula all the time when wiring houses to figure out the load for different things. The power company charges by the KILOWATT HOUR (KWH) and if you look on your power bill you can see how much they charge for this. I know the last time I looked at my bill it was somewhere in the $.14 per KWH range but I havent looked at it in some time but everyones is different. SO take the light you have and look on it to see what the wattage is to get the cost of running it. So take a 1000 watt light and for it to use 1 KILOWATT HOUR (KWH) it has to be on for 1 hour so thats where you hear all the time or see on your bill you used X amount of KWH or KILOWATT HOURS. So if you are paying say $.14 per KWH your 1000 watt light would cost you $.14 per hour to run. A KWH is 1000 watts of power for 1 hour of useage. It doesnt seem like a lot but times that per day @ 24 hours then 30 days a month and it will cost you $3.36 per day or $100.80 per month @ $.14 pewr KWH. Someone said to just save the difference by not useing power for something else well that is going to be hard to do because that light will be on all the time and other electric items are not on that long of a time or use this amout of wattage. Also if you use a 600 watt lamp you can figure out the useage the same way that 600 watt lamp if on for 1 hour would use .6 KWH then times that by 24 which would cost $2.02 per day or $60.48 per month. All my figures are based on $.14 per KWH so find you power bill and see how much they charge you and then you can see what your light will cost. Plus the power companys add other charges onto this amount with taxes and surcharges for other stuff also but at lease this way you can get an idea how much your power bill will jump.
Hope this helps anyone wanting to know about how much there light will cost and also dont forget to add in any FANS into the mix.