Quote:

Originally Posted by **burch76** 1 kwh is equal to a 100 watt bulb runnung for 10 hours.
so your dual 150 watt running for 10 hours will cost you
$0.29. multiply by 30 days it should cost you $8.70.
300x10 hours = 3 kwh x $0.097 = $0.29
Hope this is usefull |

Word, I second what burch said just multiply it out. Figure out how many hours a day you run the lights, multiply that by the number of days in a month (just approximate with 30), and multiply that by the wattage of your bulb(s), and that's your kWh. Multiply by price, and voila and pretty good estimate of price.

Kells makes a good point, the ballast, if inefficient, will end up burning a little more power than goes to your bulb. A 100W bulb will still consume 100W (I'm pretty sure), but an inefficient ballast might add some more Watts to that for your total power consumption. You could go with kells' suggestion and add 10% to your bulb wattage for a conservative estimate. Going with burch's example, assuming ballast inefficiency you're up to $9.60 a month. Still under 10 bucks, probably not going to break your bank if you own a saltwater tank lol.