3 Bedroom house, Central AC running couple hrs/day while my little girl playing down stair, her window AC running pretty much 24/7. 480g display, 250g sump 3x400w MH 4hrs/day, ATB 4200 150w, H&S protein skimmer 300w, 750w heater $200/month last month. We use 1280 Kw last month... :D