How Long Will My Heating Oil Last?

Heating oil carries about 138,500 BTU per gallon, and your burner's nozzle tells you the burn rate: a typical residential nozzle is 0.75–1.0 gallons per hour while firing. The burner doesn't fire constantly — duty cycle is what turns nozzle size into days.

Quick estimate: in mild weather (around 40°F) a typical home burns 2–4 gallons a day; in a hard freeze (around 15°F or below) 6–9 gallons a day is normal, more for large or leaky houses. So 100 gallons is roughly a month of shoulder-season heat or two cold-snap weeks.

Your own number beats any rule of thumb: stick the tank (or read a working gauge) on the same day two weeks apart, convert both readings with your tank chart, and divide. That gallons-per-day figure, taken in similar weather, is the most accurate forecast you can get without a flow meter.

Then set a reorder trigger: days remaining = gallons left ÷ your daily burn, and call when that drops near your supplier's delivery lead time plus a storm buffer. At a quarter tank on a 275 (about 11 inches), you have roughly 65 gallons — one to three weeks depending on the weather.