My two sims live in a pretty normal sized house. 3 bedrooms (only one has stuff in it because they haven't had kids yet) and I had the thermostat on for two days and my bills were 125,000 and they only had average jobs and had only about 4,000 in their account. I had to cheat just so they could pay their bills. All my other families that have the thermostat have normal bills ranging from 4,000 to 7,000 but never that much. Let's just say I turned that thing off asap. Now they just warm themselves with the fire.