One of my houses in Milwaukee had a large oil furnace. The first year I lived there I know the tank was full when I moved in. Sometime in early January the heat stopped and it took a while but I finally figured out that the tank was empty. Only thing is that it was not the standard 275 gallon tank but a 1000 gallon underground tank. I found out that the furnace had a 4.5 Gallon per hour nozzle in it. That is 630,000 BTU per hour or about 10 times what the average house has. Sure glad I won't be getting that $7000 fuel bill!