power consumption question

[Dale]

I am actually trying to figure out the power consumption of my system. I think the formula is right but I'm not sure if I'm forgetting to factor in volts or amps. I really am electrically challenged.
Another example is my lighting. If I have a 20 watt actinic on for 12Hr's/day is the calculation: 20w x 12Hr's x 31 days = 7440w / 1000 = 7.44 KwH or... am I suppose to factor in 120 volts some where?

[cprowler]

They have this calculator over at the evil empire.

http://reefcentral.com/calc/tank_elec_calc.php

[Dale]

Thanks Bill