Row home? Assuming they have tenants? I showed up at rental once and they had the windows open in the middle of the winter.
5 bedrooms is pretty big house, probably in the 3000 sq ft. range.
The average usage I've seen over the years is about 5 tons per 2000 sq. foot but that figure is going to vary widely. I had one customer in an old farmhouse presumably with no insulation and really old single pane windows. House was maybe 1500 to 2000 sq. ft. and they went through about 20 to 25 ton a year.
I've seen people in newer homes with good insulation, new windows and 6 inch walls use as little as 3 tons in same size house.