Heating Oil Cost Calculator
Yearly heating oil cost, delivered heat in MMBtu, and cost per MMBtu from gallons, price, and AFUE.
What it does
Heating oil is sold by the gallon, but the bill does not tell you what the heat costs. Two homes can burn the same number of gallons and get very different comfort if one has a 70% furnace and the other has a 90% condensing boiler. This calculator converts the fuel bill into delivered heat so the comparison is fair.
The tool takes yearly volume, the price you pay, and the furnace annual fuel utilization efficiency, usually written AFUE on the rating plate. It returns the yearly cost, the useful heat in MMBtu or kilowatt hours, and the cost of each unit of heat. The default case is 600 gallons at $4.25 per gallon through an 85% furnace.
The energy content comes from the US Energy Information Administration, which lists distillate fuel oil at about 137,381 Btu per gallon. A furnace cannot capture all of that. An 85% AFUE unit turns 85% into heat for the house and sends the rest up the flue. That is why the delivered total is lower than the raw fuel energy and why efficiency changes the cost per MMBtu.
The cost per MMBtu result is the useful number for shopping. Propane, natural gas, electricity, and wood are all priced in different units, so the only clean way to rank them is dollars per million Btu of delivered heat. Once you have that figure, a heat pump quote or a propane contract can be judged on the same scale.
Oil prices move with the season and with world crude markets. A single average price gives a planning number, not a guarantee. Homes that buy on a budget plan or fill the tank in summer usually pay less than homes that call for a delivery in January.
How to use
- Leave the unit system on Imperial for US gallons or switch to Metric for liters.
- Enter the gallons or liters your household burns in a heating season.
- Type the delivered price per gallon or liter, including taxes and delivery fees.
- Find AFUE on the furnace or boiler label and enter it as a percent.
- Read the yearly cost first, then the delivered heat and the cost per MMBtu.
- Enter a second efficiency or price to see how much a new furnace or a summer fill would change the total.
Formula
- V
- Yearly heating oil volume in gallons, or liters converted to gallons.
- price
- Delivered fuel price per gallon or per liter.
- AFUE
- Annual fuel utilization efficiency of the furnace or boiler, in percent.
- 137,381
- Btu in one gallon of distillate heating oil, from EIA.
- MMBtu
- One million Btu, the common unit for comparing fuel heat.
Metric mode converts liters to gallons with 3.785411784 L per gallon and reports delivered heat in kilowatt hours using 3,412.14 Btu per kWh. The efficiency applies to the fuel energy, so a 90% furnace delivers 90% of the Btu in the tank. The tool does not add tank rental, service contracts, or chimney work.
Worked example
Example: 600 gallons at $4.25 through an 85% furnace
Imperial defaults: 600 gal, $4.25 per gallon, 85% AFUE.
- Yearly cost: 600 x $4.25 = $2,550.00.
- Raw fuel energy: 600 x 137,381 = 82,428,600 Btu.
- Useful heat: 82,428,600 x 0.85 = 70,064,310 Btu, or 70.06 MMBtu.
- Heat lost up the flue: 82,428,600 - 70,064,310 = 12,364,290 Btu, about 15%.
- Cost per MMBtu: $2,550.00 / 70.0643 = $36.40.
- Same heat in kilowatt hours: 70,064,310 / 3,412.14 = 20,534 kWh.
Reference table
| AFUE | Delivered heat | Cost per MMBtu | Heat lost |
|---|---|---|---|
| 70% | 57.70 MMBtu | $44.19 | 30% |
| 80% | 65.94 MMBtu | $38.67 | 20% |
| 85% | 70.06 MMBtu | $36.40 | 15% |
| 90% | 74.19 MMBtu | $34.37 | 10% |
Limits
- Uses one average price and one efficiency for the whole season, not month by month deliveries.
- Ignores tank rental, burner service, chimney liners, and any electric power the burner uses.
- Assumes the furnace is tuned and the nozzle is sized for the house; a dirty burner delivers less than its rating.
- Treats 137,381 Btu per gallon as fixed, while actual batches vary slightly with blend and temperature.
Common mistakes
- Comparing the price per gallon with propane or natural gas without converting to cost per MMBtu.
- Using the AFUE from a new furnace brochure instead of the label on the unit in the basement.
- Forgetting delivery fees, tank rental, and taxes when entering the price.
- Assuming a 90% furnace saves 90% of the old bill; the saving is only the efficiency gap, about 5 points from 85% to 90%.
- Budgeting on the cheapest summer fill and then paying winter prices for the rest of the season.
Try it yourself
Quick checks. Answers sit tucked under each question.
500 gallons at $4.50 through an 80% furnace?
Cost $2,250.00, fuel 500 gal, delivered heat 54.95 MMBtu, $40.94 per MMBtu.
1,500 liters at $1.10 per liter through a 90% boiler?
Cost $1,650.00, fuel 1,500 L, delivered heat 14,359 kWh, $0.1149 per kWh.
100 gallons at $5.00 through an 81% furnace?
Cost $500.00, fuel 100 gal, delivered heat 11.13 MMBtu, $44.93 per MMBtu.
Questions
How much heat is in a gallon of heating oil?
The EIA conversion factor is about 137,381 Btu per gallon of distillate fuel oil. A furnace then captures only its AFUE share.
What is a good AFUE for an oil furnace?
New oil furnaces commonly run 80% to 86%, and condensing units can reach the low 90s. Anything near 70% is old enough that replacement often pays.
How many gallons does a house use in a year?
Many US oil heated homes use 500 to 800 gallons, but climate, house size, insulation, and thermostat habits move that range a lot.
Why does cost per MMBtu matter?
It puts oil, propane, natural gas, and electricity on one scale. Comparing price per gallon with price per therm tells you nothing useful.
Does the calculator include the electric bill?
No. It covers fuel only. A furnace blower, indirect water heater, and controls add a modest amount of electricity on top.
Should I switch to a heat pump?
Compare the heat pump cost per MMBtu at your electric rate with this result, then factor in installation, rebates, and how well the house holds heat in cold weather.
Sources
- US Energy Information Administration: Heating oil explained
- US Energy Information Administration: Energy conversion calculators
- US Energy Information Administration: How to compare the cost of heating fuels