Well my friend just dropped by so I asked him again. He said that you had to check inside of your Ballast for some kind of number. He said that the Power Supply hides the start up of the lamp which is when the power company sees the spike on your meter. As long as the battery backup is powerful enough for the light..<the reason for the expensive one>. That way the ballast draws the start up power off the battery which is then recharged through out the day. This is just another precaution for growers. Nothing more nothing less. Hope this clears it up