I was thinking more of this formula

# of luminares x total W per luminare x Annual operating hrs x Energy cost per KWH= First year energy cost/1000

Knowing amperage is not accurate enough. There is input amps and out put amps. Example, a 400w MH fixture has a total input of about 465W Amperage on ballast is not accurate in my experience. Need to measure True Power (watts)

Last edited by ayrton; 12/16/07 01:52 PM.