Propane vs. Natural Gas vs. Oil Heat: Which Costs Less to Run in Maine?

Quick answer: No fuel is always cheapest. Compare cost per BTU, not per gallon: divide your price by the fuel’s heat content (about 144,000 BTU per gallon of oil, 91,500 per gallon of propane, 100,000 per therm of natural gas), then adjust for your equipment’s efficiency. Natural gas isn’t available at every address, and a cold-climate heat pump with Efficiency Maine rebates is worth pricing too.

“Which fuel is cheapest to heat with?” is one of the most common questions we get, and the honest answer is: it depends on current prices, which move throughout the year and vary by town. What we can give you is the framework to run the comparison yourself, any time you want an up-to-date answer.

Start With BTU Content, Not Price Per Gallon

The number on your fuel bill isn’t the whole story — different fuels pack different amounts of heat energy per unit, so you have to compare cost per BTU, not cost per gallon or per therm. As a baseline:

• Heating oil: roughly 144,000 BTU per gallon
• Propane: roughly 91,500 BTU per gallon
• Natural gas: 100,000 BTU per therm (a therm is a standard billing unit, not a volume — your utility bill will already be in therms or hundreds of cubic feet)

To compare real cost, divide the price you’re quoted by the BTU content, then factor in your equipment’s efficiency (a modern 95% AFUE system gets more usable heat out of the same BTUs than an old 65% AFUE unit). It’s a bit of arithmetic, but it’s the only way to get an apples-to-apples answer instead of an apples-to-oranges one.

Why We Won’t Just Tell You “Gas Is Cheaper” or “Oil Is Cheaper”

Because it genuinely changes. Oil and propane prices swing with global and regional supply, sometimes within the same heating season. Natural gas, where available, tends to be more price-stable since it’s piped rather than delivered, but it’s not always the cheapest option depending on the year. Anyone who gives you a flat “X is always cheaper” answer is either guessing or working from stale numbers. When we quote a system, we look at current local pricing for your specific situation rather than a rule of thumb.

The One Factor That Isn’t About Price

Natural gas isn’t available at every address in our service area — utility lines don’t reach every property in Maine and New Hampshire, particularly outside village centers. If natural gas isn’t at your street, the real comparison is between oil and propane, not all three. We can tell you what’s available at your address.

Don’t Forget the Fourth Option

If you’re comparing fuel costs because you’re facing a system replacement anyway, it’s worth also pricing out a heat pump — electricity isn’t a combustion fuel, so it doesn’t fit neatly into the BTU comparison above, but a correctly sized cold-climate heat pump can be the lowest-cost-per-BTU option once Efficiency Maine rebates are factored in. We’ve written more on whether a heat pump is worth it in a Maine winter if you want to weigh that option too.

Thinking About Switching Fuels?

If oil is what you’re moving away from, see our Oil to Gas Conversion guide for what that process involves. Either way, contact us for a real comparison based on current pricing and your home’s actual heat loss — call Maine at (207)-613-6886 or New Hampshire at (603)-662-2809.