@Jane Kim
Another thing could be to do an energy audit. How good is the insulation, windows and doors. You could check if the house is losing heat via these areas.
It seems you also occupy the home so it might be fairly easy to assess electricity/heating in the general areas.
For example, I had an older tenant that would constantly open the kitchen window while cooking and the central heat was on. Had another that liked to open his window to let fresh air in his room (he was a smoker). Some people take excessively long hot showers, leave all the lights on, TV etc.
You might want to call a 'house meeting', get everyone on board to manage expectations then document after the meeting with addendum to your lease for increased utilities beyond an agreed wattage use.
Finally, see if there is a fixed payment plan offered by your provider or reduced rate for a agreed term or switch providers.
I once had a bill for over $550, I asked for consideration, turns out there was a one-time allotment. I paid almost half the bill, the company paid the rest and then I went on budget billing at $125 monthly.
Goodluck