Heating oil is a petroleum-based fuel used to heat homes and buildings, most commonly in the northeastern United States. It’s a middle-weight distillate refined from crude oil, sitting between lighter fuels like gasoline and heavier ones like lubricating oil. A single gallon contains about 138,500 BTUs of energy, making it one of the most energy-dense residential fuels available.
How Heating Oil Is Made
Crude oil is separated into different products through a process called fractional distillation, which essentially sorts hydrocarbons by weight in a tall column (around 150 feet). Lighter gases rise to the top, while heavier substances settle toward the bottom. Heating oil comes from the middle of that column, distilling at roughly 175 to 275 degrees Celsius alongside kerosene, diesel, and jet fuel.
The final product is a blend of straight-run and catalytically cracked distillates, meaning some of it comes directly from distillation and some is processed further to break down heavier molecules. Chemically, it’s a mix of hydrocarbons in the C11 to C20 range. About 69 to 79% of those are paraffins (waxy, chain-like molecules), and 19 to 25% are aromatic hydrocarbons. It also contains small amounts of sulfur, traditionally between 0.4 and 0.7%.
Heating Oil vs. Diesel Fuel
Heating oil and diesel are essentially the same product with different legal designations. Both are distillate fuels with nearly identical chemical compositions. The key differences are regulatory, not chemical.
Heating oil is dyed red. The IRS requires this so inspectors can identify fuel that’s exempt from federal, state, and local road taxes. Using red-dyed heating oil in a vehicle that drives on public roads is illegal, because you’d be dodging fuel taxes. Diesel sold at gas stations is clear or slightly green and carries those road taxes built into the price. The energy content is nearly identical: 138,500 BTUs per gallon for heating oil versus 137,381 for diesel.
Energy Content Compared to Other Fuels
One reason heating oil remains popular is its energy density. At 138,500 BTUs per gallon, it packs significantly more energy than propane, which delivers only 91,452 BTUs per gallon. That means you need roughly 1.5 gallons of propane to match the heat output of a single gallon of heating oil. Gasoline, for reference, contains about 120,214 BTUs per gallon, though it’s never used for home heating.
This high energy density means heating oil systems can warm a house quickly, which is part of why they’ve remained a staple in cold-climate regions where temperatures drop fast and stay low for months.
Sulfur Standards and Cleaner Formulations
Older heating oil was a relatively dirty fuel, with sulfur content up to 0.5% by weight. Burning high-sulfur oil produces sulfur dioxide, which contributes to acid rain and respiratory problems. Over the past decade, regulations have pushed the industry toward ultra-low sulfur heating oil (ULSHO), which caps sulfur at just 15 parts per million.
New York led this shift in 2012, becoming the first state to require ULSHO. Delaware and New Jersey followed in 2016, and all six New England states transitioned by July 2018. The change mirrors what happened with diesel fuel for vehicles, where the EPA phased in the same 15 ppm standard starting in 2006. Lower sulfur content also reduces buildup inside your furnace and extends the life of heating equipment.
Bioheat: The Renewable Blend
A growing share of heating oil sold today is blended with biodiesel, a renewable fuel made from sources like soybean oil or recycled cooking grease. These blends are marketed as Bioheat. The two most common formulations are B10 (10% biodiesel, 90% traditional heating oil) and B20 (20% biodiesel, 80% traditional heating oil).
The environmental case is significant. On a lifecycle basis, biodiesel can cut carbon emissions by up to 86% compared to straight petroleum. Even a B20 blend makes a measurable difference. New York City officials have estimated that widespread B20 use has the equivalent impact of taking thousands of cars off the road. Biodiesel also burns with far less soot and sulfur, which means cleaner exhaust and less residue inside your heating system. Most modern oil furnaces and boilers can run B20 blends without any modifications.
What Drives Heating Oil Prices
Heating oil prices generally track crude oil prices, since crude is the raw material. Worldwide supply and demand set that baseline, and it shifts based on weather events, geopolitical tensions, and production decisions by OPEC members. But even when crude prices hold steady, heating oil tends to get more expensive between October and March, when demand peaks during the heating season.
Local factors matter too. The number of suppliers in your area affects price competition. If you live in a rural region with only one or two dealers, you’ll likely pay more than someone in a suburban area with several options. Delivery costs also vary. Getting fuel to remote locations is more expensive, and those costs get passed to the customer. Watching prices and locking in a rate before winter starts is one of the most effective ways to manage your annual heating budget.
Home Storage Tanks
Unlike natural gas, which arrives through a utility pipeline, heating oil is delivered by truck and stored in a tank on your property. Most residential tanks hold 275 gallons, though sizes vary. Tanks can be installed above ground (in a basement, garage, or outside) or buried underground.
Aboveground tanks typically last 25 to 30 years, sometimes longer with proper care. Underground tanks have a shorter expected lifespan of 15 to 20 years, largely because they’re exposed to soil moisture and harder to inspect. How long your tank actually lasts depends on whether it was installed correctly, how often it’s been serviced, and the local environment.
Signs of a failing tank include visible rust spots or denting, moisture forming on the tank’s surface, oil on the floor beneath the tank, wobbly or corroded legs, and cracked fuel lines. A leaking tank is both an environmental hazard and an expensive cleanup problem, so catching deterioration early is worth the effort. Having your tank inspected every few years, especially if it’s more than 15 years old, can save you from a costly surprise.
Where Heating Oil Is Most Common
Heating oil use is heavily concentrated in the Northeast. States like Connecticut, Maine, Vermont, New Hampshire, and Massachusetts have some of the highest rates of oil heat in the country, a legacy of the region’s older housing stock and the infrastructure built around oil delivery decades ago. Many of these homes were built before natural gas pipelines reached their neighborhoods, and converting to a different fuel source requires significant upfront investment. For millions of households, heating oil remains the practical, reliable choice for getting through winter.