Propane Cost For Average Home. A 1,500 square foot home in a mild climate would require approximately 1.5 million BTUs of propane fuel for heating each month. Based on a cost per gallon of $2.86, it would cost approximately $57 per month to heat the home with propane. The same size home in a moderate climate would require 3 million BTUs per month, and cost $114. A home in a severe climate would need about 5 million BTUs per month, and cost approximately $191 per month to heat.