how much energy does a hps light use
Report Abuse. Your 400 watt hps lamp will operate at 468 watts if you include the ballast. If you run it at 120 volts and if you live in the Midwest, it should cost around 8 cent per hour to run. The hps is not a grow lamp so you will not get anything to grow under this lamp. Hps is the worst on the color spectrum for light output.