sounds like you're getting charged too much for power puttputt, i have same lighting and a heap more devices that suck power than your tank (from what i can see) and mine works out about $100 - $130 a month, of that the lights use about $60 a month. so out of a $480 power bill, thats 1/4 of my usage approx. hot water is the biggest killer in our house. get a centameter - worth their weight in gold