Estimate how many days of fuel are left in your tank, when it needs refilling, and what the fill will cost. Using the 10-year normal for January (27.2 degree days a day) and a typical K-factor of 5.5, a home burns about 4.9 gallons a day in midwinter — so a three-quarter-full 275-gallon tank lasts roughly 38 days. Heating oil last surveyed at $5.535/gal, propane at $2.674/gal.
EIA surveys heating oil and propane prices only during the October–March heating season. The prices above are from 2026-03-30, about 151 days ago, and are almost certainly not today's market. Enter your own price below for a realistic cost.
Days of fuel remaining, from your tank level and the weather.
Formula: gallons per day = degree days per day ÷ K-factor; days left = usable gallons ÷ gallons per day. Usable volume is taken as 90% of nameplate — tanks are not filled to the roof and the bottom inches sit below the outlet.
What a delivery costs at today's price.
Switching fuel changes only the seeded price — the tank arithmetic is identical. Propane holds less energy per gallon than heating oil (0.0915 vs 0.1385 MMBtu), so a propane home burns noticeably more gallons for the same warmth; compare them properly on the heating cost calculator.
Home heating demand is close to linear in degree days, and that is the whole reason the industry measures them. A day averaging 45°F produces 20 heating degree days; one averaging 5°F produces 60. The colder day demands roughly three times the fuel, and the ratio holds well enough that delivery companies schedule trucks on it without inspecting anyone's tank.
That is also why a single gallons-per-day figure misleads. Across a season the US average swings from a handful of degree days in October to more than 900 in January — so a burn rate calibrated in autumn under-predicts midwinter consumption by a wide margin, and the tank empties weeks before the estimate said it would. Expressing the rate per degree day removes the seasonality and leaves a number that describes your house rather than the month.
The K-factor is that number. Divide the degree days accumulated between two deliveries by the gallons delivered and you have a personalised figure that accounts for insulation, thermostat habits, house size and boiler efficiency all at once. Recompute it after each delivery and the estimate gets steadily better — and a K-factor that drifts lower over time is a useful early hint that something has degraded, whether a failing boiler or a draught that has opened up.
It depends far more on the weather than on the house. A 275-gallon tank holds about 240 usable gallons, since tanks are never filled to the top and the last few inches sit below the outlet. A typical home burning 4 to 6 gallons a day in a cold January empties a full tank in roughly six to eight weeks. The same house in mild October weather might use under a gallon a day and go all month on a fifth of a tank.
A K-factor is the number of heating degree days your home burns per gallon of fuel — a single number describing how efficiently the building holds heat. Divide the degree days accumulated between two deliveries by the gallons delivered and you have it. Most houses land between 4 and 8. A lower K-factor means a draughtier or larger home that burns more fuel for the same weather. Delivery companies use exactly this to schedule automatic refills without ever visiting the tank.
Because fuel use tracks the weather almost linearly, and the weather changes by a factor of ten across a heating season. A fixed daily rate that is right in January will be badly wrong in November. Degree days measure how far each day fell below 65°F, so a burn rate expressed per degree day stays valid all season — which is why the industry schedules deliveries on them.
Most suppliers suggest ordering at about a quarter tank, which on a 275-gallon tank means roughly 70 gallons — usually one to two weeks of cold-weather supply, and enough buffer to survive a cold snap or a delivery backlog. Running a tank truly empty is worth avoiding beyond the inconvenience: it can draw sediment into the fuel line and an oil system generally needs bleeding and restarting by a technician.
They are the EIA state and regional averages for fuel delivered to residential customers, which is the right benchmark but not a quote. Your delivered price varies with volume, whether you are on a contract or a will-call basis, how far you are from the depot, and the day you order. EIA also surveys these fuels only during the October-to-March heating season, so an off-season figure on this page is the last one collected, not a current price.