I have a 1600 square foot house built in 1910 on pier and skirt foundation with block and brick at points, insulation is key here. We keep the house at 64° in the winter time and things get a little chilly due to insulation inconsistencies in the old walls. If OP is throwing real numbers here, then insulation or potentially an open air gap is causing his loss of heat and increase in bill. The electric company also doubled the cost of electricity between 2019 and today.