I used a dual tube 4' T8 6000k ballast for veg then switched to a 400w HPS and using two of the dual 4' T8's 3500k for veg.My electric bill at 400w 12hours on at 10 cents per kw/h went up around $15
https://www.rollitup.org/indoor-growing/71346-my-first-real-indoor-grow.html