Propane vs heating oil: cost per year
A gallon of heating oil holds 1.51 times the energy of a gallon of propane, so the price per gallon cannot be compared directly. At the example prices ($5.97 a gallon for oil, $3.54 for propane, week of October 12, 2026) and the boiler efficiencies below (Efficiency Maine's defaults, as on the cost calculator), heat costs about $49.55 per million Btu from oil and $41.62 from propane. A home that burns 1,000 gallons of oil a year would need about 1,417 gallons of propane for the same heat.
What the same heat costs, by oil gallons per year
Each row starts from the oil a house burns in a year and works out the propane that would deliver the same heat. Oil at 87% efficiency, propane at 93%.
| Oil per year | Heat delivered | Oil cost | Propane gallons | Propane cost | Oil minus propane |
|---|---|---|---|---|---|
| 500 gal | 60.2 MMBtu | $2,985 | 708 gal | $2,508 | $477 |
| 750 gal | 90.4 MMBtu | $4,478 | 1,063 gal | $3,761 | $717 |
| 1,000 gal | 120.5 MMBtu | $5,970 | 1,417 gal | $5,015 | $955 |
| 1,250 gal | 150.6 MMBtu | $7,463 | 1,771 gal | $6,269 | $1,194 |
| 1,500 gal | 180.7 MMBtu | $8,955 | 2,125 gal | $7,523 | $1,432 |
A positive last column means propane would cost less at these prices. Prices are EIA residential averages for Maine, excluding taxes. Your dealer's price will differ.
The arithmetic
oil: 138,500 Btu × 87% = 120,495 Btu delivered per gal
propane: 91,452 Btu × 93% = 85,050 Btu delivered per gal
1 gal oil = 1.42 gal propane
1,000 gal oil × 120,495 = 120.5 MMBtu
The heat contents are EIA's sample Btu conversion factors: 138,500 Btu per gallon for heating oil and 91,452 for propane. The example prices are EIA's weekly residential prices for Maine (heating oil, propane). The efficiencies are the defaults of the cost comparison calculator. The table is my own arithmetic from those inputs.
Break-even propane price
The propane price per gallon that gives the same cost per million Btu delivered as oil at the price in the first column. A propane quote below the number means propane is cheaper for that pair of boilers. The columns change the efficiency of each boiler (oil % / propane %).
| Oil price | 87% / 93% | 80% / 93% | 87% / 80% | 80% / 80% |
|---|---|---|---|---|
| $4.00 | $2.82 | $3.07 | $2.43 | $2.64 |
| $4.50 | $3.18 | $3.45 | $2.73 | $2.97 |
| $5.00 | $3.53 | $3.84 | $3.04 | $3.30 |
| $5.50 | $3.88 | $4.22 | $3.34 | $3.63 |
| $6.00 | $4.24 | $4.61 | $3.64 | $3.96 |
| $6.50 | $4.59 | $4.99 | $3.95 | $4.29 |
| $7.00 | $4.94 | $5.37 | $4.25 | $4.62 |
Reading it: with oil at $6.00 and both boilers at the calculator defaults, propane breaks even at $4.24 a gallon. A quote under that makes propane the cheaper fuel for heat, and a quote over it favors oil.
What these numbers leave out
The comparison covers fuel only. A switch also costs a new boiler or furnace, a propane tank (often leased from the dealer) and a chimney or vent change, and none of that is in the table. In a HeatingHelp forum thread a poster says a customer who switched from oil to propane told him she never spent so much to heat her house, and sums it up as "It's all about the cost of fuel". That is one anecdote, and it fits the break-even table: the answer follows the local prices of both fuels.
Related pages
Put in your own prices and efficiencies on the heating fuel cost comparison. To estimate your yearly oil gallons first, see heating oil usage per month, or propane use per month. For a heat pump instead, see heat pump vs oil.