Given a 4,000 watt load on 24 hours a day and an actual cost of $0.06 per kWh: Kw = Kilowatt - a measure of electrical power (watts) equal to 1,000 watts. In G.E. descriptions, also “M” is used cf. 1M/T12/CL. kWh = Kilowatt Hour, The standard measure of electrical energy and the tipical billing unit used by utilities for electricity use. A 100-watt lamp operated for 10 hours consumes 1000 watt-hours or 1 kilowatt hour. If the utility charges $0.10 / kWh, than the electricity cost for the 10 hours of operation would be 10 cents. (GE Catalog) How much does it cost per day to run these lights? This is one that came up at work today to which I gave the info out on how to determine, but was way to busy in doing an 8 hour project in 5 hours to sit down and do the math for the person that asked. (My constant dumb as a box of rocks “best friend” when he needs something he should know.) Last week on a different project it was a question of how many Lumens a 8' high output fluorescent tube gave out. But than it was discovered that the LED fixtures to replace them gave candlepower in having a directional beam not Lumens thus I had to find that conversion chart which only halfway works as a conversion. Again too busy to do the math for those making the commission much less paid to figure it out. Given it's what such people get paid to know how to do anyway. I know this stuff why don’t you given it’s what you do for a living the constant question in my head. I fix stuff and buy lamps, the designers answer client questions and sell the product. Life should be so well defined. It was unfortunately beyond the ability of the designer and the young college kid he asked to do the math for him, thus it is still un-answered. Anyone like story problems? There is a 55 story condo wishing to know how much his design will cost - ya think? I’m curious but not enough to put any time into it.