Reasonable Electric and Gas Bill

My Mom lives in Westchester County, NY, and I'm trying to get a sense of what a fairly reasonable electric & gas bill is, since I think ConEd may be way overcharging her. Her last bill was for $400 for one month. She lives in a split-level private home, and I'm estimating it has between 2000 and 2500 square feet (I'm mentally mapping it against my condo, which I know has 1000 square feet). So, let's say 2500 square feet.

It has single-paned windows (not good for heat retention), but she keeps the lights off throughout most of the house except for the room she is in. She also still works, so she is not home during the day. The also keeps the temperature down throughout the house, around say 65 to 70 degrees, and uses those small oil-filled heaters to heat just the room she stays in. Her main energy consumption is the kitchen, which of course has a refrigerator, a dishwasher she does not use all that often, a computer that's on constantly. (Don't even ask why the computer is in the kitchen.) T.V. is in use sometimes, there is a printer, and of course washer and drying as needed.

She only takes a bath once a day, and always uses cold water to wash her clothes. I'd say the amount of cooking she does is moderate.

Overall, she just doesn't use that much electricity. I tend to come up and visit once a month, and stay for four days, sometimes a bit longer. When I'm up, I will crank up the heat (gas fuel, electric motor).

Overall, $400 seems like a lot of money. However, it's hard for me to judge. I live in a condo where all utilities are commonly metered and rolled into the condo fee, so I can't compare her utility bills with my own. So, I'm curious if people can tell me -- especially people with roughly 2000 to 3000 square feet of living space -- what your utility bills are. Please also indicate (approximate) geographic area, so I can see if things are very different in, say, Oklahoma compared to New York.

Thanks in advance for all replies.

CJ