How many square feet does 48000 BTU heat in a gas furnace?

Answer 1

48,000 input or output? If 48K is the input to an 80% efficient furnace, than the output would only be 38,400. It also depends on where the house is located, because 48K will heat a much larger house in Miami than it would in Minneapolis. You need to post more info to get a worthwhile answer. But to give you an idea I heat 1000 sq ft in NJ easily with a 52,500 80% efficient furnace which yields 42,000 output.