Running HPS lights need some knowledge!!

I have been bowfishing for about 8 years now. 5 years ago I bought the 150watt HPS lights. I have been running them ever since.

I currently run 5 HPS lights off a 2000 Honda Generator. I can only pull 4 lights at first and then I can plug the 5th one up. I would like to buy one or two more my HPS lights but I don't know if my generator will pull them. I believe it will pull one more but I would hate to spend the money if it won't work. It has everything to do with the amps it uses I just don't know how many amps lights pull when they are heated up.

THANKS.