My Mother's house is about 4,200 sq feet, built in 1903.
The only bill that's outrages is the heating, primarily because it's oil fired. Electric is about $120 a month, averaged out.
So, to average $2,500 a month, he's either in an insanely priced area, or he's running the heat and air conditioning at the same time 24x7 and leaving every light on in the house all the time.