Calculating energy costs

[edit24k]

I had a guide once but lost it, which helped you calculate predicted energy costs for powering hps light over a period, anyone able to assist?

[the image reaper]

multiply the watts, x the hours per day ... multiply that x number of days ... multiply that x your electric rate (let's say 12.3 cents per megawatt) ... divide that x 1000 = $$ ... example: 400 watts x 18 hours per day = 7200 ... 7200 x 30 days = 216,000 ... 216, 000 x the rate (12.3 cents), = 2,656,800 ... divided by 1000 = $26.57 rounded-off ... :smokin: