The short answer
If you are thinking about converting your home from heating oil to propane, do the BTU math before you compare prices. A gallon of heating oil holds about 138,500 BTUs of energy, while a gallon of propane holds only about 91,500 BTUs. That means it takes roughly 1.5 gallons of propane to produce the same heat as one gallon of oil. So a propane price that looks lower per gallon may not actually be cheaper once you account for how much less heat each gallon delivers.
Why a gallon is not a gallon
Heating fuels are not created equal. What actually heats your home is energy, measured in BTUs (British Thermal Units), not the volume of liquid in the tank. Because heating oil is a denser, more energy-rich fuel, each gallon does noticeably more heating work than a gallon of propane.
- Heating oil: about 138,500 BTUs per gallon
- Propane: about 91,500 BTUs per gallon
Divide one by the other and you get roughly 1.5. In plain terms: to replace the heat from 1 gallon of oil, you would burn about 1.5 gallons of propane. Over a full winter, that difference adds up fast.
The comparison that actually matters
Because of that energy gap, comparing the two fuels by their sticker price per gallon is misleading. The fair way to compare is on an equal-heat basis. There are two simple ways to do it:
- Multiply the propane price by about 1.5 and compare that number to the price of a gallon of oil, or
- Convert both to a cost per 100,000 BTUs (or per million BTUs) so you are comparing the same amount of heat.
A quick example
Suppose heating oil is priced at $3.50 a gallon and propane is priced at $3.00 a gallon. At first glance propane looks like the better deal. But to match the heat of one gallon of oil, you need about 1.5 gallons of propane:
- 1 gallon of oil: $3.50
- 1.5 gallons of propane (equal heat): 1.5 x $3.00 = $4.50
On an equal-heat basis, the oil is actually the better value in this example, even though propane had the lower price per gallon. Prices move constantly, so always run the numbers with current rates, but the principle holds: you have to normalize for BTUs.
Don’t forget the cost to convert
Switching fuels is not just a matter of price per gallon. Converting from oil to propane means new equipment and installation, which is a significant upfront expense:
- A new propane furnace or boiler, since oil equipment cannot burn propane.
- A propane storage tank, either leased or purchased, plus lines and regulators.
- Removal or decommissioning of your existing oil tank in some cases.
- Professional installation and permitting.
Those costs can take many years to recover, if they are recovered at all, especially once the BTU difference is factored into your ongoing fuel bills.
Modern oil heat is efficient, too
Some homeowners assume switching fuels automatically means big efficiency gains. In reality, a well-maintained, modern oil furnace or boiler is clean-burning and efficient, with high-efficiency oil systems reaching AFUE ratings comparable to gas equipment. An annual tune-up keeps an oil system running at its best, often making a conversion unnecessary.
When does propane make sense?
Propane is a good option in some situations, mainly where heating oil is not practical or where a homeowner specifically wants gas appliances for cooking, a fireplace, or a generator. But if you already heat with oil and your system is in good shape, the combination of the BTU penalty and the upfront conversion cost means switching often does not pay off. The honest way to decide is to compare current, equal-heat prices and weigh them against the cost to convert.
Frequently asked questions
How many gallons of propane equal a gallon of heating oil?
About 1.5 gallons. Heating oil holds roughly 138,500 BTUs per gallon and propane about 91,500, so it takes approximately one and a half gallons of propane to match the heat of a single gallon of oil.
Is propane cheaper than heating oil?
Not necessarily. It depends on current prices compared on an equal-heat basis. Because propane delivers fewer BTUs per gallon, you have to multiply its per-gallon price by about 1.5 before comparing it to oil. A lower price per gallon does not automatically mean a lower heating bill.
Does converting from oil to propane cost money upfront?
Yes. Converting requires new heating equipment, a propane tank, lines, and professional installation, which is a substantial upfront investment that can take years to recoup.
Is modern oil heat efficient?
Yes. Today’s oil furnaces and boilers are clean-burning and efficient, and high-efficiency models rival gas equipment. Annual service keeps an oil system operating at peak efficiency.
Before you convert, get the real numbers
If a propane sales pitch has you considering a switch, run the BTU math first and factor in the cost to convert. We are happy to give you a current heating oil price so you can compare honestly, on an equal-heat basis. Call us at (215) 874-0093, and remember we offer weekday same-day heating oil delivery when you order by noon in Bucks County, Montgomery County, and Philadelphia.