If you've been wondering whether to switch from oil to gas — or whether you're already overpaying — you're not alone. It's one of the most common questions Nassau County homeowners ask, especially after a rough winter bill. The short answer is that gas does cost less per unit of heat at current prices. But the full answer is more complicated, and most of what you'll read online either oversells the savings or dismisses them entirely. We've been delivering heating oil to Nassau County homes for over 40 years, so we've seen this debate from every angle. Here's what the data actually shows.
Cost of Gas vs. Oil Heat: The Real Per-BTU Breakdown
The most honest way to compare heating fuels is by cost per unit of heat — specifically, per million BTUs. One gallon of heating oil contains about 138,700 BTUs. One therm of natural gas contains about 100,000 BTUs. That means to match the heat output of a single gallon of oil, you'd need roughly 1.4 therms of gas — about 40% more gas by volume.
At recent national average prices, heating oil runs approximately $37.30 per million BTUs, while natural gas comes in around $9.20 per million BTUs. That's a real gap. On a typical Nassau County home burning 800 gallons of heating oil per season, the annual fuel cost difference can reach $1,450 or more. Over ten years, that adds up to roughly $14,500 in fuel savings — if everything else stayed equal. It doesn't, but we'll get to that.
Natural Gas vs. Oil Heat Cost: What Efficiency Ratings Actually Mean
You'll often see furnace efficiency described in AFUE ratings — Annual Fuel Utilization Efficiency. A 98% AFUE gas furnace converts 98 cents of every dollar of fuel into usable heat. Modern oil furnaces run between 84% and 95% AFUE. Older, unmaintained units can fall into the 60s.
That efficiency gap is real, and it does widen the cost difference somewhat. But it doesn't widen it as much as the raw AFUE numbers suggest, because oil's higher BTU density per unit partially offsets it. You're burning less volume of oil to produce the same heat, even if gas converts a higher percentage of its fuel.
The net result is still a cost advantage for gas at current prices — just not as dramatic as a headline comparison of AFUE ratings alone would imply. Here's the part that often gets left out: gas furnaces typically need replacement after 11 to 14 years. A well-maintained oil furnace can last 20 years or more. That longer replacement cycle matters when you're calculating total ownership cost over time.
A gas system that saves you money on fuel but requires replacement every 12 years may not save as much as it looks on paper. There's another line item most gas-conversion articles skip: the fixed monthly service charge from National Grid, which runs $20 to $40 per month before you burn a single therm. That's $240 to $480 per year in baseline utility costs that oil customers don't pay.
None of this means gas is the wrong choice. For many Nassau County homeowners, it genuinely is the better long-term option. But the math is more nuanced than a per-BTU comparison, and anyone telling you otherwise is selling something.
Is Oil Heat More Expensive Than Gas? What Nassau County Homeowners Should Factor In
For most Nassau County homes, yes — heating oil costs more per unit of heat than natural gas at current prices. That's the honest answer. But whether it's worth switching is a different question entirely, and the answer depends heavily on your specific situation.
The conversion from oil to gas on Long Island typically runs between $8,000 and $18,000 total installed. That includes removing your oil tank (above-ground removal runs $500 to $1,500; underground abandonment can reach $5,000), installing a new gas heating system ($4,000 to $8,000 for a furnace, $6,000 to $12,000 for a boiler), and any gas piping or flue liner work the job requires. At $1,200 to $1,450 per year in fuel savings, you're looking at a payback period of roughly 7 to 15 years — assuming prices hold and everything goes smoothly.
That payback math changes significantly depending on a few things. First: how old is your current oil system? If it's 5 years old and running well, you're paying the full conversion cost on top of a working system. If it's 20 years old and due for replacement anyway, the incremental cost of going to gas is just the difference between a new oil system and a new gas system — which is a much more favorable comparison. Second: how long do you plan to stay in the house? A 10-year payback period doesn't make sense if you're planning to sell in five. Third: is gas actually available at your specific address? Most of Nassau County has National Grid service, but not every home is connected. You can check at nationalgridus.com before you go any further.
There's also a competitive advantage worth addressing directly. Many homeowners assume oil customers have no leverage over prices — that you're at the mercy of the market. That's actually less true for oil than for gas. Natural gas is a utility monopoly. You buy from National Grid at whatever rate they set. Heating oil customers can shop multiple suppliers, buy in the off-season when prices are lower, lock in rates through price protection plans, or prepay before winter. That competitive dynamic is one of oil heat's underappreciated advantages, and it's one reason the cost gap between the two fuels narrows considerably for homeowners who manage their oil purchases strategically.
Is Oil Heat More Expensive Than Gas When You Factor In Bioheat?
The environmental argument has long been one of gas's strongest selling points over oil. But that argument has changed significantly — and most comparison guides haven't caught up yet.
As of July 2025, every gallon of heating oil sold in New York State must contain at least 10% biodiesel. That's B10 Bioheat — a blend that includes renewable fuel derived from vegetable oils, animal fats, and recycled cooking grease. By 2030, that minimum rises to 20%. Every OK Petroleum delivery in Nassau County already meets this standard. No equipment modifications required, no action needed on your part — it's just what heating oil is now.
What the New York Bioheat Mandate Means for Nassau County Oil Heat Users
The B10 mandate is part of New York's broader push toward cleaner energy, and it applies across Nassau County, Suffolk County, New York City, and Westchester. The biodiesel component significantly reduces particulate emissions and sulfur output compared to conventional heating oil. The gap between oil and gas on environmental grounds — which was real a decade ago — is narrowing with each increase in the biodiesel blend requirement.
What most Nassau County homeowners don't know is that the Bioheat mandate also comes with a financial benefit. New York State offers a Clean Heating Fuel Tax Credit of up to $0.20 per gallon for Bioheat fuel containing at least 6% biodiesel. Since Nassau County's heating oil is already B10, every customer who heats with oil is eligible to claim this credit. On 800 gallons per heating season, that's up to $160 back in your pocket — claimed through Form IT-241-I on your state return. It's not a fortune, but it's a real number that most oil customers are leaving on the table simply because they don't know it exists.
The broader point is this: if part of your reason for considering a gas conversion is the environmental footprint of heating oil, it's worth knowing that the fuel being delivered to your tank today is meaningfully different from what it was five or ten years ago. And by the time Nassau County reaches B20 in 2030, the environmental calculus will look different still.
Nassau County's Housing Stock and Why the Conversion Decision Is More Local Than You Think
Nassau County's median home was built around 1955. Levittown, Bethpage, Rockville Centre, Garden City, Wantagh, Plainview, Massapequa, Merrick — these communities are defined by postwar Cape Cods, split-levels, and ranch homes that were built around oil heat from the ground up. That's not a coincidence. When these neighborhoods were developed in the late 1940s and 1950s, natural gas infrastructure across most of Long Island was limited or nonexistent. Oil-fired boilers and furnaces were the standard, and the homes were designed around them.
That history matters for two practical reasons. First, these homes already have the infrastructure for oil heat — existing tanks, compatible boiler rooms, and flue configurations that work with oil equipment. Converting to gas means not just replacing the appliance but potentially reconfiguring the mechanical room, removing the oil tank, running new gas piping, and pulling permits. That's where the $8,000 to $18,000 range comes from, and it's why the same conversion that might pencil out in one home might not in another.
Second, Nassau County's housing stock means that a large number of oil heating systems across the county are reaching the end of their natural lifespan right now. A 1970s-era boiler in a Hicksville split-level or a Seaford Cape Cod is due for replacement whether the homeowner switches fuels or not. And that's actually the moment when the gas conversion math looks most favorable — when you're already facing a system replacement, the incremental cost of going to gas is just the difference between a new oil system and a new gas system, not the full $8,000 to $18,000 on top of a working setup.
If you're in that position — old system, considering your options — the honest advice is to get quotes for both. Compare a high-efficiency oil boiler (84% to 95% AFUE) against a gas conversion with the full installed cost included. Run the payback math at current prices. And factor in how long you plan to stay in the house. That's the decision framework that actually serves you, rather than a headline number that oversimplifies it.
Gas vs. Oil Heating Cost on Long Island: What Should You Actually Do?
Here's the honest summary. Natural gas costs less per BTU than heating oil at current prices — that's real, and it's not going away. For homeowners with an aging system, gas already on the street, and a long-term plan to stay in the house, conversion is worth running the numbers on seriously. For everyone else, the math is more complicated than the headlines suggest.
What's also true is that heating oil in Nassau County today is cleaner than it's ever been, the competitive pricing dynamic still favors oil customers who shop strategically, and a well-maintained oil system can serve a Long Island home for 20 years or more. Neither fuel wins every comparison. The right answer depends on your home, your system, and your plans.
If you're staying on oil — or if you've run the numbers and decided conversion doesn't make sense right now — we're here. OK Petroleum Distribution has been delivering to Nassau County and Suffolk County homes since 1976, and we offer both automatic delivery and no-contract will-call service, online ordering, and multiple payment options including budget plans and price protection. Give us a call at (631) 321-0549 and we'll help you figure out what makes the most sense for your home.
